M.M: 80. Time:2hr
Section-A ( 40 marks)
Q1 MCQ (1×15=15 marks)
Q2 short question answer (2×6=12 marks)
Q3 short question answers (13 marks)
Section -B (40 marks)
Attempt any four questions:
Q4 (1+2+3+4=10 marks)
Q5 (1+2+3+4=10 marks)
Q6. (1+2+3+4=10 marks)
Q7. (1+2+3+4=10 marks)
Q8. (1+2+3+4=10 marks)
Sub- physics
Class-7
M.M: 80
Time: 2hrs
Section-A(50 marks)
Answer all questions.
Q1 fill in the blanks: (10)
1.1 the image formed by a plane mirror is at a distance behind the mirror as........
1.2 we are able to see objects around us due to........ Reflection.
1.3 a ...... Image cannot be obtained on screen.
1.4 a plane mirror......... Reflects 100% light falling on it.
1.5 blue, Red and green are the........ Colours.
1.6 on heating a body, it's temperature.........
1.7 the SI unit of temperature is........
1.8 the temperature of a normal human body is....... °C.
1.9 heat transfer in solids is by........
1.10 black and Dull surfaces are........ Of heat.
Q2. Write true or false for each statement: (10)
(10)
2.12.1 all solids expand by the same amount when heated to the same rising temperature.
2.2 water is bad conductor of heat.
2.3 kerosene contracts on heating.
2.4 black surfaces are poor absorbers of heat radiations.
2.5 medium is necessary for the transfer of heat radiation.
2.6 the image formed by a plane mirror is upright.
2.7 the image formed by a plane mirror can be obtained on a screen.
2.8 a rose appears red in light of all the colours.
2.9 the speed of light in vacuum is 3× 10⁶ ms-¹.
2.10 the image formed by plane mirror is lateral inverted.
Q3. Match the following: (10)
3.1 light ray passes from air to glass. A. Speed up
3.2 virtual image. B. Reflects red light.
3.3 A light ray passes from glass to water C. plane mirror
3.4 red rose. D. Secondary colours
3.5 magenta, yellow & cyan E. slows down
3.6 Mercury. F. Insulator
3.7 wood. G. Water from 0°C to 4°C.
3.8 aluminium. H. Absorbs
3.9 contracts. I. Conductor
3.10 black surface. J. Thermometer
Q4. Answer the following questions: (2×10=20)
4.1 what is heat? State its SI unit.
4.2 name the two scales of temperature. How are they interrelated?
4.3 why do telephone wires sag in summer? Explain.
4.4 what are good and bad conductors of heat? Give examples of each.
4.5 what are land and sea Breezes?
4.6 state the laws of reflection of light.
4.7 state two uses of a plane mirror.
4.8 write down the letter C & D as seen in a plane mirror.
4.9 the leaves appears green in white light. How will it appear in green and red light?
4.10 convert - 40°C to the °F scale.
Section-B(30 marks)
Answer any three questions:
Q5.1 draw a ray diagram showing the formation of image of a point object by a plane mirror.
5.2 write four differences between real and virtual image. (6+4=10)
Q6.1 state any four characteristics of the image formed by a plane mirror. (4)
6.2 fill in the blanks with appropriate colour: (3)
A. Blue + ......... = Cyan
B. ........, + ...... = Magenta
C. ........ + Blue = white.
6.3 state the speed of light in (3)
A.air
B. Glass
C. Water
Q7.1 draw a neat labelled diagram of a thermos flask. How the transfer of heat by conduction , convection and radiation is reduced? (6)
7.2 name the mode of transfer of heat in the following: (4)
A. Liquid
B. Vacuum
C. Gas
D. Solid
Q8.1 describe an experiment to show that liquids expand on heating. (3+1+2+4=10)
8.2 define temperature.
8.3 draw a neat level diagram of a laboratory thermometer.
8.4 the temperature of a body Rises by 1°C. What is the corresponding rise on the:
A. Fahrenheit scale
B. Kelvin scale?
Class Test / Class work = 10 marks + 10 marks
= 20 marks
Weekly Test = 20 marks
First term exam = 60 marks
First term exam Result = CT + WT + First term exam
= (20 + 20 + 60 ) marks
= 100 marks
1. Four fundamental physical quantities are as follows:
A.length-fixed distance between two points.
Its SI unit is metre.(m)
B.Mass- quantity of matter contained in a body.
Its SI unit is kilogram.(kg)
C.Time- interval between two consecutive events.
Its SI unit is second.(s)
D.Temperature- degree of hotness or coldness of a body.
Its SI unit is kelvin.(K)
2.No. it is not possible to measure volume of a body by using a graph paper or graphical method because by using graph paper we can find area of a body. Further area and volume are two different physical quantities. So ,Same method cannot be used to find two different physical quantities.
3.Given,
Base area =150 m²
height of the table=12m
Total of the table & box = 25m
Volume of the box= ?
Height of the cuboid box= total height - table's height
= 25m - 12m
=13m
Volume of the box= l×b×h
= area × h
= 150 m² × 13 m
=1950 m³
4. Density of water is maximum at 4 degree Celsius. Density of water decreases when it is cooled from 4 degree Celsius to 0 degree Celsius or heated above 4°C.
Yes. It is going to affect the volume of water.
Density = mass / volume.
Density is inversely proportional to volume.
Since density decreases,so it means volume will increase.
5. Liquid displacement method is a method in which ,we find the volume of an irregular shaped body by putting it in a measuring cylinder which is partially filled with liquid.the object should be completely immersed in liquid.then we note down reading
V = final reading while object is in measuring cyllinder - initial reading of cyllinder without the object.
V = V² - V¹
6. Mercury is used as a barometric substance because its density is more than the density of water.so, height of the Mercury column required to balance the atmospheric pressure is 76 cm but in case of water the height of the water column required will be a 10.34m which is a difficult task to maintain. Hence mercury is preferred as a barometric liquid.
1. Draw the circuit diagram for a series combination of two bulbs namely A and B connected to a battery of two cells, a resistor,two switches and 1 fan connected parallel to two bulbs A and B.
2. How will you ensure your continuous supply of current? Explain it.
3. Why steel cannot be used as core of an electromagnet instead of soft iron?
4. What do you mean by an electrical circuit? Name its essential components and explain their functions. Illustrate it with the help of suitable diagram.
5. Which terminal is represented by the metal cap of a dry cell? Draw its well labelled diagram and explain it.
6. Who and when discovered the magnetic effect of current? Explain the working principle of an electric bell with the help of a suitable diagram.
7. Why do metals conduct charges better than plastic?
8. State four advantages of electromagnets over permanent magnets.
9. Distinguish between following:
A. Open and closed circuit.
B. DC current and AC current
C. Conductor and insulator
D. Permanent magnet and an electromagnet
10. What is a sure test for magnetism? How is the direction of electric current related to the direction of flow of electrons? Why do we get current only for a short, while we connect a negatively charged ebonite rod to A positively charged glass rod?
1. The deepest part of the ocean is the Marina Trench located in the Pacific Ocean, whose depth is 11033 m. If you were on a ship above this trench and send a sound signal straight down to the water, how long will it take for the Echo to reach you. Speed of sound in water is 1450 metre per second.
2. Find the time period of a pendulum which is vibrating at 12 Hz?
3. We can predict the arrival of a train by placing our ears on the rail without seeing it. How it is possible. Explain it.
4. The sound of thunder is heard after the lightning is seen.why?
5. What do you mean by the loudness of sound? On what what factors does the loudness of sound depends?
6. Show that sound is a non- electromagnetic wave.
7. In the outer space, a number of explosions and vibrations of material objects may be taking place all the time but they do not produce any effect on the human ears. Give the reason for this. Why should we consider this as a blessing in disguise for all life on the earth?
8. Give one example for the following:
A. Frequency of the sound produced may be changed without any change in its loudness.
B. Loudness Of the sound produced any significant change in its frequency.
9. How A vibrating body produces longitudinal waves in air.explain it with the example of a tuning fork.
10. Pendulum B makes 20 oscillations in 5 seconds and pendulum Q makes 8 oscillations in 4 seconds. Which has higher frequency? Express the frequency of each pendulum in Hz.
1. Rishav puts a stainless steel spoon in a glass of Hot Milk but Arnav does not do so. The milk of which glass will cool faster. Give reasons for your answer.
2. Why woollen clothes are better than cotton clothes in winter?
3. What would be the final temperature difference between two bodies after they have been in contact with each other for quite some time?
4. A man of mass 84 kg, maybe e regarded as having done a work of 8.4 kilojoule while climbing up stairs that take him to a height of 10m above the ground. Suppose the man I want to burn out 48 kcal by repeatedly climbing up the stairs. Neglecting the loss or gain of energy by him while climbing down, estimate the number of 'upward trips' that he needs to make.
5. Shyam's mother is fond of shining vessels, thought of replacing her cooking vessels with vessels that were shining bright on all sides.But Ashok's mother told her that she should not do so. She told her that shining metal caps are good for fire fighters but vessels, with shining bottoms are not good for cooking. What do you think? Give reasons for your answer.
6. Is it it true to say that liquids are not only expand on heating but they do so more than solids? Explain.
7. What happens to a hot body when put in air? Explain it in detail.
8. Why on a wintry day a metallic object appears colder than a wooden one?
9. Why should we not rely on our sense of touch for estimating the hotness of an object? Explain it on the basis of your Physics textbook.
10. How will you find the range of a clinical thermometer? Explain why a clinical thermometer cannot be used to measure high temperatures?
1. A person is sitting on a chair in a dark room near one of the walls. A big mirror is hung on the wall facing the person. When a torch light is put on the person from a distance, then we can see P of of the the person on the wall behind him . At the same time Q of the person can be observed in the mirror on the wall.
A. What is P ?
B. What is Q?
C. State one way in which P differs from Q.
2. State the colour of Red shirt in a room illuminated by a green light only. Give reason for your answer.
3. Man moves towards a plane mirror with a speed of 4 metre per second. How fast is his image moving towards him?
4. Explain the observed colours of
A. a cyan object in yellow light
B. a red object in Magenta light
5. What do you understand by a pigment? Explain it with an example.
6 . Why "ambulance" is written reverse on the ambulance vehicle?
7. A person is standing 1.7m away in front of a plane mirror. Where is the image formed? How much is the distance between him and the image.
8. Explain both types of reflection of light with the help of a suitable example.
9. How will you prove that light is composed of seven colours?
10. The angle formed between a reflecting surface and the reflected ray is 20 degree. Find angle formed between incident ray and the reflected ray?
1. Define four fundamental quantities of measurement and mention their Si units with symbol.
2. Is it possible to measure the volume of an irregular stone by using graph paper. Justify your answer.
3. A cuboid box whose base area is 150m². It has been kept on a table of height 12m. The total height of the table and box's top is 25m. Find the volume of the box?
4. The density of water is maximum at 4 degree Celsius. It decreases when it is cooled from 4 degree Celsius to zero degree Celsius or it is heated above 4 degree Celsius. Is it going to to affect volume of water?explain.
5. What do you mean by liquid displacement method? How it can be used to measure relative density of a solid body?
6. why Mercury is used in a barometer as a barometric liquid instead of water?
7. The longest chord of a park is 196m. Find the perimeter of the park and then its area.
8. A truck travels for 60 minutes with a constant speed of 54 km per hour. Find the distance travelled by it? Express your answer in SI and CGS unit.
9. A a truck Travels with a speed 18 metre per second and car with a speed of 72 kmh‐1. Which travel faster and by how much?
10. Can you measure 35 cm³ of water by using a measuring cylinder of capacity 100 ml?explain it with the help of a suitable example.
1. A person X travelling in a car with a speed of 60 km per hour. Another person Y who is 100m behind X , claims that the first person X is at rest. Is it possible? Justify your answer.
2. Differentiate between uniform motion and non uniform motion. Write three differences. Explain with the help of suitable example.
3. Distinguish between rotatory motion and translatory motion with the help of suitable examples. Write three points.
4. Distinguish between following:
A. Rectilinear motion and curvilinear motion.
B. Circular motion and rotatory motion.
C. Oscillatory motion and vibratory motion.
D. Periodic motion and non periodic motion.
5. Distinguish between mass and weight . Write five differences.
6. A person goes from his office to another City by car at a speed of 60 km per hour and returns back through the same route at a speed of 45 km per hour. Find the average speed of his journey?
7. A person x off mass 90 kg. If the pull of gravity on 1 kg on the surface of earth is 9.8 Newton and at the surface of moon is 1.6 Newton, find
A. The weight of person x on the earth.
B. The weight of the person at at the moon surface.
8. A boy Travels a distance of of 2 km in the first 2 hour, 0.5 kilometre in the third hour and 0.6 km in the fourth hour. Find the average speed of the boy in
A. Kmh-¹
B.ms-¹
9. Is it possible to measure weight of a person by using a beam balance .justify your answer. If weight cannot be measured by it, then how will you measure the weight of a person ?explain its principle.
10. State two units of speed and weight. Establish the relationship between their Si units.
1. AN object is raised to a height of 10 m above ground of mass 50 kg. If the object is allowed to fall down then find its kinetic energy when it is just about to touch the ground?
2. State different units of energy. How they are related to each other?
3. Explain how molecules ability to do work get affected while heating and cooling?
4. Establish the relationship between kilowatt hour and the SI unit of energy.
5.A car triples his speed. How will his kinetic energy change? Show it with the help of mathematical calculations.
*Energy:
•energy is the ability or capacity to do work.
• SI unit of energy is joule.
•symbol is J.
•CGS unit of energy is erg.
•another unit of energy is calorie.
Symbol is cal.
*A body is said to possess an energy of one joule if one joule work is done to bring the body in that state.
•Relationship between SI and CGS unit of energy
1J = 1N × 1m
= 1 kgm/s² × 1m ( F =mass × acceleration
F = 1kg × 1m/s²
= 1kgm/s²
=1N )
= 1×1000 g×100cm/s² × 100cm (1kg= 1000g , 1m= 100cm )
= 10⁵g.cm/s² × 10² cm
= 10⁵ dyne × 10² cm
= 10⁵+² dyne.cm
= 10⁷ erg
1 J = 10⁷ erg
1 erg = 1/10⁷ J
= 10-⁷ J
•Relationship between 1J and 1 calorie
1cal = 4.186 J
1 cal ≈ 4.2 J
1J =0.24 cal
•Relationship between kilo calorie and calorie
1 kcal = 1000 cal
1 cal = 1/1000 kcal
= 10-³ kcal
* Work:
•Work is said to be done, when a force is applied on the body and the body gets displaced or moved.
•work done= force applied × distance moved in the direction of force.
work = force × displacement
• SI unit of work is J.
1 joule of work is said to be done when a force of 1 Newton moves a body by a distance of 1 metre in the direction of force.
• CGS unit of work is erg.
1 erg of work is said to be done when a force of 1 dyne moves a body by a distance of 1 cm in the direction of force.
• SI unit of force is Newton.
•CGS unit of force is dyne.
1 N = 10⁵ dyne.
1.Which is not an example of an oscillatory motion
Ans.Earth's Revolution around the sun.
2.Which is is not an example of of vibratory motion
Ans.Motion of a charkha
3.which is Not an example of periodic motion
Ans.None of these.
4.Which among the following is odd one
Ans.Moon's Revolution around the earth
5.Pick the odd one among the following
Ans.A carpenter's saw
6.Which is not an example of a circular motion
Ans.None of these.
7.A boy goes from his house to school by bus at a speed of 40 kilometre per hour and returns back through the same route at a speed of 30 kilometre per hour. The average speed of his journey is
Ans. Take the LCM of 40 and 30 = 120
Take it as distance =120 km
T₁=120km/40 kmh-¹
= 3h
T₂= 120km/30kmh-¹
= 4h
Average speed=total distance travelled/total time taken
= (120km + 120km)/(3h+4h)
= 240 km/ 7h
= 34.285 kmh-¹
8.Which statement is false
Ans.Mass always acts vertically downwards.
9.Weight of a body is 600N on the surface of moon. What would be the weight of the body on the earth surface?
Ans.3600N
10.A car moves a distance of 30 km in 2 hours. what is the speed of the car in S.I. unit?
Ans. Speed=distance/time
= 30km/ 2h
=15 kmh-¹
= 15× 1kmh-¹
= 15×5/18 ms-¹
= 75/18 ms-1
=4.16666 ms-¹
≈4.17 ms-¹
11.A bus is running at a constant speed of 60 km per hour. What will be the distance covered by the bus in 20 minutes?
Ans. Speed=60km/h
Time=20 minutes
=20×1 minute
= 20× 1/60 h
=1/3 h
Distance=?
Speed=distance/time.
Speed×time= distance
Distance= speed×time
= 60 kmh-¹ × 1/3 h
= 20 km.
12.Rajdhani express leaves New Delhi at 4:30 p.m. and reaches Ranchi that is at a distance of about 1000 kilometre at 3:30 a.m. the next day. Find its speed?
Ans. Time between 4:30 p.m. to 3:30 a.m.=11 h
Distance travelled= 1000km
Speed=?
Speed=distance/time.
= 1000km/ 11h
= 90.909090 kmh-¹
≈91 kmh-¹.
13.Find the time taken by a train moving at 80 kilometre per hour to cover 600 kilometre?
Ans. Speed=distance/time
Speed×time= distance
Time=distance/speed
= 600 km /80kmh-¹
= 60/8 h
=60/8 × 60 minutes
= 3600/8 minutes
= 450 minutes.
14.The motion of the earth is
Ans.Periodic motion
15.The motion of a pendulum shows
Ans.Oscillatory motion
16.ms-¹ is used to measure
Ans.Speed
17.Nkg-¹ is the unit of
Ans.Acceleration due to gravity
18.The weight of a a boy is 60 Kgf. His mass will be
Ans.60kg
19.A ball falls down vertically. Its motion is
Ans.Translatory motion
20.If a body covers equal distances in in unequal interval of time, motion is said to be
Ans.Non- uniform motion
1.What remains constant if a stone falls from a height at a particular place?
Ans. Acceleration due to gravity remains constant at a particular place. It is represented with small 'g'.
g=9.8ms-²
≈10ms-²
2.the motion of the wheels of a bicycle is an example of........ type of motion.
Ans. Mixed motion/complex motion.
The motion of The wheels of a bicycles shows two types of motion simultaneously.
Rotatory motion as well as translatory motion.
3.Which one is odd among the following
Ans.A ball thrown by a boy.
Because it shows curvilinear motion.Where as the other threes are examples of rectilinear or linear motion.
4.A man sitting in a moving train is at rest with respect to
Ans.Fellow passengers
5.The the weight of a body is zero
Ans.At the centre of earth
6. A man completes 4 complete round along the the boundary of a rectangular field 30m long and 20 metre wide in 5minutes & 20 seconds. find his speed?
Ans. Perimeter=2(l+b)
Distance covered in 4 round= 4× 2(l+ b)
= 4× 2(30m+20m)
= 4×2(50m)
=4×100m
=400m.
Time taken= 5 minutes & 20 seconds.
=5×60s + 20s
= 300s + 20 s
= 320s.
Speed=distance/time.
= 400m/320s
=40m/32s
=5m/4s
=1.25ms-¹.
7.If a body covers 10m, 15m and 20m in three successive seconds. calculate the average speed of the body
Ans.d₁=10m
t₁= 1s
d₂= 15m
t₂=1s
d₃=20m
t₃=1s
Average speed=total distance travelled/total time taken.
=(10m + 15m + 20m ) / (1s+1s+1s)
= 45m / 3s
= 15ms-¹
8.Weight of a box on the the earth surface is 120 Newton .what would be its weight on the Moon surface
Ans. Weight of a body on earth surface is 120 N.
Weight of a body on the moon surface= (1/6)th of weight of box on earth's surface
= 1/6 × 120 N
= 20N
9.A man Travels from Ranchi to Ramgarh with a constant speed of 50 kilometre per hour and returns from Ramgarh to Ranchi with a constant speed of 40 kilometre per hour. find the average speed of the man
Ans. Take the LCM of speed of man.
LCM of 40 & 50 would come as 200.
Take distance as 200km.find t₁& t₂
Speed= distance/time
Speed×time= distance.
Time=distance/speed
t₁= 200km/ 50kmh-¹
= 4 h
t₂= 200km/40kmh-¹
= 5h
Average speed= distance travelled /time taken
Average speed=( 200km + 200km )/ (4h + 5h)
= 400km / 9 h
= 44.44kmh-¹
= 44.44× 1km/h
= 44.44 × 5/18 ms-¹
=12.3444 ms-¹
10.If a body covers equal distances in an unequal intervals of time the motion is said to be
Ans.non-uniform motion.
11.Which of the following is a periodic motion?
Ans.Pendulum oscillations & Motion of the earth.
So, the correct option is (C). both a and b
12.Weight is a
Ans.Vector quantity.
because weight has both magnitude as well as direction
13.The motion of an object that covers equal distances in equal intervals of time is called
Ans.Uniform motion
14.Which of the following is not an example of periodic motion
Ans. Mosquito flying in a random direction.
1. The length, breadth and height of a water tank are 5.0 m, 2.5 metre and 1.25 metre respectively .calculate the capacity of the water tank in a) m³ b)Litre
Ans. Dimensions of of a water tank is given as length=5.0m , breadth=2.5m height=1.25m
V=l×b×h
V=5.0m×2.5m×1.25m
=15.625m³
Once again ,
V=5×100 cm ×2.5×100×1.25×100cm (1m=100cm)
=500cm×250cm×125cm
=15625000cm³
=15625×1000cm³
=15625 ×1L (1000cm³= 1L)
=15625L.
2. A solid silver piece is immersed in water contained in a measuring cylinder .the level of water rises from 50 ml to 62 ml .find the volume of silver piece?
Ans. Liquid displacement method for finding volume of a solid body is used.
V1=50 ml ,V2=62ml
V=V2 -V1
V=62ml -50ml
=12ml
=12× 1ml
=12×1cm³ (1ml=1cm³)
=12cm³.
3. Find the volume of a liquid present in a disc of dimensions 10 cm×10cm×5cm?
Ans. Dimension given means l=10cm, b=10cm, & h=5cm.
V=l×b×h
V=10cm×10cm×5cm
=500cm³
=500×1cm³
=500mL (1cm³=1mL)
4. A rectangular field is of length 60 m and breadth 35m . find the area of the field?
Ans.l=60m, b=35m
A=l×b
A=60m×35m
=2100m²
5. Find the approximate area of an irregular lamina of which boundary line is drawn on the graph paper shown in figure 1.16 below.
Ans. Graphical method of finding area of a an irregular lamina is to be used.
A=No. of complete boxes + No. of half boxes and more than half .
A=10 complete boxes + 11 more than half boxes
=21 boxes
=21×1 box
=21 cm². (Area of 1 box=1cm²)
6.A piece of brass of volume 30 cm³ has a mass of 252 gram. find the density of brass in a)gcm³. b)kgm³
Ans. Given,
V=30cm³, M=252g
Density= M/V
Density= 252g/30cm³
=8.4 gcm-³
In terms of SI unit of density,
Density=8.4× 1 gcm-³
=8.4× 1000kgm-³. (1gcm-³=1000kgm-³)
= 8400 kgm-³
7. The the mass of an iron ball is 312 gram. The density of iron is 7.8 gram per centimetre cube. Find the volume of the ball?
Ans. Given ,
M=312g. Density=7.8gcm-³
Density=mass/volume.
Density×volume=mass
volume=mass/density
= 312 g/7.8 gcm-³
=40 cm³.
8. A cork has a volume 25 cm-³. The density of crop is 0.25 gram per centimetre cube. Find the mass of the cork?
Ans. Given,
Volume=25cm-³.
Density=0.25gcm-³
Mass=?
Density=mass/volume
Density×volume=mass
Mass=density×volume
Mass=0.25 gcm-³ × 25 cm³
=6.25 g.
9. The mass of 5 litre of water is 5 kg.find the density of water in gram per centimetre cube?
Ans. Given,
Mass=5.0 kg
=5.0× 1.0 kg
=5.0 × 1000g. (1 kg=1000g)
=5000 g.
Volume=5.0 L
=5.0 × 1L
= 5.0 × 1000cm³. (1L=1000cm³)
=5000 cm³
Density=mass/volume.
Density=5000g/5000cm³
=1 gcm-³.
10. A cubical tank of side 1m field with 800 kg of a liquid. Find: a) the volume of tank b) the density of liquid in kgm-³.
Ans. Given,
Cube of side 1 metre.
Volume of a cube=s×s×s
Volume=1m×1m×1m
= 1m³.
Density=mass/volume.
Density=800kg/1m³
=800 kgm-³.
11. A block of iron has dimensions 2m×0.5 m×0.25m. the density of iron is 7.8 gcm-³. Find the mass of block?
Ans. Given,
Dimensions as l=2.0m, b=0.5m & h=0.25m
V=l×b×h
V=2.0m×0.5m×0.25m
=0.25m-³
Density=7.8 gcm-³
=7.8× 1 gcm-³
=7.8× 1000 kgm-³
=7800 kgm-³
Mass=?
Density=mass/volume.
Density×volume=mass
Mass=density×volume
= 7800 kgm-³ × 0.25 m-³
=1950kg.
12. The mass of a lead piece is 115 g. When it is immersed into a measuring cylinder, the water level rises from 20 ml mark to 30ml mark. Find
a) the volume of lead piece,
b) the density of the lead in kgm-³.
Ans. given,
Mass=115 g.
Volume to be calculated by liquid displacement method.
V2=30 mL. , V1=20 mL
V =V2 - V1
V=30mL - 20 mL
=10 mL.
=10×1mL
=10 × 1cm³. (1mL=1cm³)
= 10 cm³
Density=mass/volume.
Density=115 g/10 cm³
=11.5 gcm-³
=11.5 × 1 gcm-³
=11.5 × 1000 kgm-³. (1gcm-³= 1000 kgm-³)
=11500 kgm-³.
13. The density of copper is 8.9 g cm-3. What will be its density in kgm-³?
Ans. Density of copper is 8.9gcm-³
In S.I unit density of copper=8.9× 1 gcm-³
=8.9×1000kgm-³ (1gcm-³=1000 kgm-³)
=8900 kgm-³.
14. A car travels a distance of 15 kilometre in 20 minutes find the speed of the car in a) kmh-¹ b)ms-¹
Ans. Distance travelled=15 km
Time taken=20 minutes
=20× 1 minute
=20×1/60 h. (1hour=60 minutes,
1h=60×1 minutes, 1/60 h =1 minute)
=1/3 h
Speed=distance travelled/time taken
Speed=25 km / 1/3 h
=45 kmh-¹.
But ,
Speed=45 kmh-¹
=45× 1 kmh-¹
=45× 5/18 ms-¹
=12.5 ms-¹.
15. How long a train will take to travel a distance of 200 kilo metre with a speed of 60 kilometre per hour?
Ans. Given,
Distance travelled=200 km.
Speed=60 kmh-¹
Time taken=?
Speed=distance travelled/time taken
Speed×time taken=distance travel
Time taken=Distance travelled/speed
=200km/60 kmh-¹
=20/6 h
=3h + 2/6 h
=3h + 2/6 × 1h
= 3 h + 2/6 × 60 minutes. (1hour = 60 minutes)
= 3h + 2×10 minutes
= 3h + 20 minutes
=3h 20 minutes.
16. A boy travels with a speed of 10 ms-¹ for 30 minute. How much distance does he travel?
Ans. given,
Speed=10 ms-¹
Time=30 minutes
=30× 1 minute
=30× 60 s. (1 minute =60s)
= 1800 s
Distance travelled=?
Speed=distance travelled/time taken
Speed×time taken=distance travelled
distance travelled=speed×time taken
=10ms-¹ × 1800 s
=1800m
=1800×1m
=1800×1/1000 km. (1km=1000m, 1km=1000× 1m , 1/1000 km = 1 m)
=1.8 km.
17. Express 36 kmh-¹ in ms-¹.
Ans. 36 km/h = 36×1 km/h. (1km=1000m,1h=60×60s)
=36 ×1000 m / 60×60 s
=36 ×5/18 ms-¹
=2×5 ms-¹
=10 ms-¹.
18. Express 15 ms-¹ in kmh-¹
Ans.15 ms-¹ =15×1ms-¹
= 15× 18/5 kmh-¹. (1ms-¹=18/5 kmh-¹)
=3×18 kmh-¹
= 54 kmh-¹.
☆ density
• density of a substance is defined as mass per unit volume of that substance.
• density= mass/ volume.
• equal masses of different substances have different volumes.
• equal volumes of different substances have different masses.
• to distinguish between different substances we used the term called density.
• density is a scalar quantity.
• SI unit is kg/m³ or kgm-³.
• CGS unit is g/cm³ or gcm-³.
• relationship between SI unit and CGS unit of density: 1kgm/m³=1000g/1000000cm³
=1/1000 gcm-³
= 10-³ gcm-³
1gcm-³ = 1000 kg m-³
• generally density decreases with increase in temperature and increases with decrease in temperature. Because all substances expand on heating and contracts on cooling.
• water contract on on heating from 0 degree Celsius to 4 degree Celsius. This abnormal behaviour of water is known as Anomalous expansion of water.
•
The density of water is maximum at 4 degree Celsius it decreases when it is cooled from food degree Celsius to degree Celsius or it is heated above 4 degree Celsius.
☆Determination of density of regular solids:
•measures mass - by using beam balance & volume of a body by formula method
and then uses formula,
Density= mass/ volume.
☆ determination of density of an irregular solid:
• measure the mass of the given solid by using Beam balance.
• volume of an irregular solid is measured by liquid displacement method.
• after finding mass and volume.
We uses formula,
density=mass÷ volume.
☆ determination of density of a liquid:
• take a empty beaker & measure its mass as M1.
• take a measuring cylinder and add a liquid into it to a certain level say a 20 ml.i.e.,20cm³
• transfer the liquid into the empty beaker and measures its mass again as M2.
• the difference between M2 and 1 will give the mass of the liquid in gram.
M=M2 - M1
• find the density of liquid using the the formula
Density=mass/ volume.
=(M2 - M1) / V
• different substances have different densities.
• barometer used to measure atmospheric pressure makes use of Mercury because of its high density of 13.6 g/cm³.
☆ speed:
• the distance covered or travelled by a body in unit time is called the speed of the body.
•speed = distance travelled/ time taken
• SI unit of speed is m/s or ms-¹.
• CGS unit of speed is centimetre per second i.e., cm/s.
• other units of speed are as follows:
1km/h =1000m/3600s
=5/18 ms-¹
=0.27777 ms-¹
=0.28 ms-¹
1ms-¹ = 3.6 kmh-¹
• 18 kmh-¹ = 1ms-¹
•1 km/minute = 1000m/60minutes
= 100m/6minutes
=16.67 ms-¹
•1ms-¹ = 100 cms-¹
•1m/minute =100cm/60s
=1.6666 cms-¹
=1.67 cms-¹.
☆ physical quantity-
• A quantity that can be measured is called a physical quantity.
Or a measurable quantity is called a physical quantity.
• a physical quantity can be of two types:
1. Scalar quantity- which can be expressed only by their magnitude.eg. mass, length, time ,distance, density ,volume, speed, temperature, work, energy, power, pressure etc.
2. Vector quantity- which requires the magnitude as well as the direction to express them.eg. force ,weight, velocity , displacement ,acceleration,magnetic field ,moment of force etc.
• physical quantity= magnitude× unit
• basic quantities or fundamental quantities with their S.I. units:
1. Length - metre- m
2.Mass- kilogram- kg
3. Time- second-s
4. Temperature- Kelvin-K
5. Luminous intensity- candela-cd
6. Electric current- ampere-A
7. Amount of substance-mole-mol
☆ measurement-
- measurement is a comparison of an unknown quantity with a known fixed quantity of the same kind.
☆length -
• length is the distance between two points.
• SI unit is metre.
• Symbol is 'm'
• measured by measuring tape or metre ruler.
☆ mass-
• mass is the quantity of matter contained in the body.
• SI unit is kilogram.
• symbol is 'kg'
• measured by beam balance or an electronic balance.
☆ time-
• time is the interval of occurrence of an event.
Or
the interval between two instances or events is called time.
• s i Unit is second.
• symbol is 's'
• measured by pendulum clock or watch.
☆ temperature-
• temperature is A quantity which measures the hotness or coldness of a body.
• SI unit is Kelvin.
• symbol is 'K'
• measured by a thermometer.
☆ measurement of volume-
• the space occupied by an object is called its volume.
• SI unit is Cubic metre or m³.
• 1 cubic metre is the volume of a cube with each side 1 metre long.
• other units of volume
Cubic centimetre, litre,dm³,mL,etc.
• relationship between different units-
1m³=1m×1m×1m
=100cm×100cm×100cm (1m=100cm)
=1000000 cm³
=10⁶ cm³
1L=10-³ m³
1m³=1000L
1L=1000 cm³
1L=1000 mL.
1dm³=1dm×1dm×1dm
=10cm×10cm×10cm (1dm=10cm)
=1000 cm³
=1L
1L=1dm³
1mL=1cm³
☆ vessels for measuring the volume of liquids
• measuring cylinder-
• area of cross section of 10 centimetre square is is made up of either glass or plastic.
• it is is of capacity 100cm³ or 100mL.
• used in laboratory to measure the volume of liquids.
• used to find the volume of an irregular object by measuring the displacement of water or liquid by the object.
•Measuring beaker-
- used to measure a fixed volume of a liquid such as milk, oil etc.
• available in different capacities such as 50ml, 100 ml ,200 ml, 500ml ,1000ml .
☆ measurement of volume of a liquid
• by using a measuring cylinder
• by using a measuring beaker
☆ measurement of volume of regular objects
• the volume of regular object is measured by finding its three dimensions that is Length ,breadth & height or radius and then using the formula.
1 volume of a cube=side×side×side
=s³
2. Volume of a cuboid= length× breadth× height =l×b×h
=A×h (A=l×b)
3. Volume of a sphere=4 π/3 × r³
4. Volume of a cylinder=π×r²×h
5. Volume of a cone=π/3 ×r²×h ,
π=22/7 or pie=3.14
☆ measurement of volume of an irregular body-
• volume of irregular shaped body is measured by using a measuring cylinder by the method of displacement of liquid.
• volume of a body of irregular shape= volume of liquid displaced by the body when it is immersed completely into the liquid.
• the difference in the final level from the initial level gives the volume of the liquid displacedi.e., V=V2 -V1 V2=final level ,V1=initial level.
☆ area-
• The surface occupied by an object is called its area.
• SI unit of area is square metre.
• symbol is m²
• square metre is equal to the area of a square of side 1 metre.
1m²=1m×1m
• Bigger units of area are:
1 decameter² (are)=10m×10m
=100m²
=10²m²
1 hectare=100m×100m
=10000m²
=10⁴m²
1km²=1km×1km
=1000m×1000m
=10⁶m²
• smaller unit of area:
1cm²=1cm×1cm
=1/100 m ×1/100 m
=10‐²m×10-²m
=10-⁴ m²
1mm²=1mm×1mm
=10-³m×10-³m
10-⁶m²
☆ measurement of area of regular objects:
• area of a regular object can be found by measuring the two dimensions that is length breadth or radius and then using appropriate formula.
1. Area of a square=side×side
2. Area of a rectangle= length× breadth
3. Area of a circle=π×r²
4. Surface area of a cylinder=2×π×r×length
5. Surface area of a sphere=4×π×r²
π=22/7
Or π=3.14 r=radius.
☆ measurement of area of an irregular object:
• by graphical method
• place the irregular object or lamina over a graph paper and draw its boundary line on the graph paper with a pencil .
•Area= the number of complete square + the number of squares half and more than half within the boundary line.
• area of one box is 1cm².
1. Explain the meaning of the terms rest and motion.
Ans. rest- a body is said to be at rest if it does not changes its position with respect to a reference point with time.eg. a book lying on a table , a bench fixed under a tree etc.
Motion- a body is said to be in motion if it changes its position with respect to a reference point with time.eg. a moving car, a flying bird etc.
2. Comment on the statement 'rest and motion are relative terms'. give an example.
Ans. An object can be in motion relative to one set of objects while at rest relative to some other set of objects.eg. for a passenger in a moving train the other train moving with the same speed and in the same direction appears to be at rest while the train moving in the opposite direction appears to be in motion.
An object while in motion with respect to a set of objects can appear at the same time in state of rest with respect to some other set of objects moving with the same sweet and in the same direction.
3. Fill in the blanks using one of the words :at rest ,in motion.
a) a person walking in a compartment of a stationary train is....in motion... relative to the compartment and is...at rest... relative to the platform.
b) a person sitting in a compartment of a moving train is...at rest.. relative to the other person sitting by his side and is.in motion....Relative to the platform.
4. Name five different types of motion you know.
Ans. Different types of motion are as follows:
1. Translatory motion- every point of the object moves through the same distance in the same time ,then the motion of the object is called translatory motion. Example falling of an apple.
2. Rotatory motion- a body is said to be in a rotary motion if it moves about a fixed axis. Example the Blades of a fan ,a spinning top ,spinning wheel etc.
3 circular motion- the motion of a body along a circular path is called circular motion. Example the motion of a car around a circular path.
4. Oscillatory motion- to and fro motion of a body from its rest position or mean position is called the oscillatory motion. Example the motion of the pendulum of a wall clock.
5. Vibratory motion- a part of the body always remain fixed and the rest part moves to and fro about its mean position then such a motion is called as vibratory motion. Example the vibration of the membrane of a tabla when played.
6. What do you mean by translatory motion ?give one example.
Ans. A translatory motion is a motion in which every point of the object moves through the same distance in the same time. Example falling of an apple.
7. What is rotatory motion? give two examples.
Ans. A body is said to be in a rotatory motion if it moves about a fixed Axis .for example the Blades of a fan ,a spinning top, a spinning wheel or a potters wheel ,a Merry Go Round, rotation of the earth about its own axis etc.
8. What is meant by circular motion? give one example.
Ans. The motion of a body along a circular path is called circular motion. Example the motion of a satellite around the earth.
9. How does rotatory motion differ from circular motion?
Ans. In rotatory motion the axis of rotation passes from a point in the body itself whereas in circular motion the axis of revolution passes through a point outside the body. Thus, the motion of a satellite around the earth is a circular motion where as the motion of earth about its own axis is a rotational motion.
10. Explain oscillatory motion by giving one example.
Ans. The to and fro motion of a body from its rest position or mean position is called the oscillatory motion. for example the motion of the pendulum of a clock and the motion of a swing represent oscillatory motion.
11. What is vibratory motion? give one example.
Ans. A vibratory motion is a motion in which a part of the body always remains fixed and the rest parts moves to and fro about its mean position. The shape and size of the body changes. Example our vocal cords vibrate to produce sound when we speak or sing.
12. Differentiate between periodic and non periodic motions by giving an example of each.
Ans.1) A motion which get repeated after a regular interval of time is called a periodic motion. where as the motion which does not repeat itself after a regular interval of time is called periodic motion.
2) example of periodic motion a normal person's heart beats every 0.8 seconds , the pendulum of a clock repeats its motion after every two seconds. Examples of non- periodic motion a footballer running on a field ,application of brakes in a moving vehicle, a ball rolling down the ground gradually slows down and finally stops motion of the tides etc.
13. What is random motion? give an example.
Ans. A motion in which a body do not take a specific path and specific direction is called random motion. Example the the motion of particles of a liquid or a gas, mosquito flying etc.
14. Name the type of motion being performed by each of the following:
a) vehicle on a straight road
rectilinear motion/ linear motion( translatory motion)
b)Blades of an electric fan in motion
Rotatory motion
c) pendulum of a wall clock
Oscillatory motion/ periodic motion
d) smoke particles from chimney
Random motion
e)hands of a clock
Circular motion
f) earth around the sun
Curvilinear motion or circular motion,Periodic motion
g) spinning top
Rotatory motion
15. Give two examples to illustrate that a body can have two or more types of motion simultaneously.
Ans. Following are 2 examples to illustrate that a body can have two or more types of motion simultaneously:
1. A ball rolling on the ground has rotatory motion as well as translatory motion as it moves on the ground.
2. The earth rotate about its axis- rotatory motion and at the same time it revolves around the sun in a path- curvilinear or circular motion in a fixed time interval that is periodic motion.
16. State the types of motion of the following:
a) the needle of a sewing machine
Periodic motion( oscillatory motion)
b) the wheel of a bicycle
Mixed motion( translate and rotatory motion of a wheel)
c) the drill machine
mixed motion( rotatory as well as translatory motion)
d) carpenters saw
Mixed motion( oscillatory as well as translatory motion)
17. Distinguish between uniform and non uniform motion. giving an example of each.
Ans.51. If a moving body travels equal distances in equal intervals of time its motion is said to be e uniform motion. If a moving body travels an equal distances in equal intervals of time its motion is said to be non- uniform.
2. Example 1 hour moving with a constant speed is example of uniform motion. Whereas a car moving in a busy road or Market is an example of of non uniform motion.
18. How do you determine the average speed of a body in non uniform motion?
Ans. Average speed of a body= Total distance travelled ÷ total time taken
19 . Define the term weight and state its SI unit.
Ans. The the weight of a body is the force with which Earth attracts the body that is the weight of a body is the force of gravity on it.
SI unit of weight is Newton.
20. How are the units of weight ,kgf and Newton related?
Ans.1kgf=9.8N
1N=1/9.8 kgf
=0.1 kgf
21. State three differences between mass and weight.
Ans.1. Mass is the quantity of matter contained in a body. Where as weight it is the force with which the earth attracts the body.
2. The SI unit of mass is kilogram where as the SI unit of weight is Newton.
3. Mass is a constant for a body and it does not change by changing the place of the body where as weight is not constant for a body but changes from place to place.
22. Which quantity: mass or weight , does not change by change of place?
Ans. Mass is the quantity which does not change by change of place.
23. State which of the quantities mass or weight is always directed vertically downwards.
Ans. Weight is the quantity which is always directed vertically downwards towards the centre of the earth.
Second term weekly test revision questions Q1.a) what do you mean by degradation of energy? b) why a person should use bio- char stoves for...