M.M:80. Time:2hrs
Section - A(40 marks)
Q1 Fill in the blanks. (1×5=5 marks)
Q2. true/ false. (1×10= 10 marks)
Q3. Short answer questions (1×10=10 marks)
Q4. MCQ questions ((1×15=15 marks)
Section -B ( 40 marks)
Attempt any four questions:
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)
Q9. (1+2+3+4= 10 marks)
Every question has four parts.
Q1. Answer the following questions in short:
1.1 prove that light always travels in a straight line with the help of suitable activity or example.
1.2 why is the image formed in a pinhole camera?
1.3 define umbra. Explain the formation of shadows by small source of light.
1.4 explain why,we often see bright circular patches of light on the ground under a tree on a sunny day?
1.5 what conclusion do you get from the fact that when an object is placed in the path of light, a shadow is formed behind the object?
1.6 what is a pinhole camera? Explain its working and principle with the help of a suitable well labelled diagram.
1.7 what is an annular solar eclipse? State three conditions of its occurrence.
1.8 why flying objects like aeroplane and birds do not cast shadow on the earth surface? Explain it with the help of suitable diagram.
1.9 although moon is a non luminous body but yet it shines during the night time. Explain it the help of suitable diagram.
1.10 define following terms:
A. Light
B. Natural source of light
C. Artificial source of light
D. Bio luminescence
E. Ray of light
F. Parallel beam of light
G. Convergence beam of light
H. Divergence beam of light
I. Beam of light
J. Translucent object
Q2. Descriptive questions:
2.1 what are eclipses? Write the difference between lunar and solar eclipse.
2.2 what are the factors that affect the size of the image produced by a pinhole camera?
2.3 write the characteristics of image formed by the pinhole camera. Write four points.
2.4 what do you mean by partial solar eclipse?
2.5what do you mean by diamond ring? State the conditions of its occurrence.
Q3. Give reasons for the following:
3.1 we get a lunar eclipse only during a full moon.
3.2 we do not get a solar eclipse on every new moon day.
3.3 we do not see any shadow of a bird flying high up in the sky.
3.4we get both the umbra and the penempura regions in the shadow of an opaque object when we use a finite source of light.
3.5 we see and inverted image of the object on the screen of a pinhole camera.
Q4. Distinguish between:
4.1 solar eclipse and lunar eclipse.
4.2 natural source and artificial source of light.
4.3 umbra and penumbra
4.4 convergence and divergence beam of light.
4.5 translucent ,transparent and opaque objects.
Q5 encircle the odd one and give the reasons:
5.1 wooden board, butter paper, stone, book
5.2 water, glass, air ,frosted glass
5.3 electric bulb, Sun ,candle ,book.
5.4 paper bag, water bottle, pencil box, firefly.
5.5 pinhole camera, formation of shadows, scattered sunlight, eclipses.
Q6 choose the correct option:
6.1 we can see objects in a bright room because:
A. The objects give off light to the air
B. The objects send light away from our eyes
C. Our eyes give off light to the objects
D. The objects reflect the light falling on them.
6.2 in which of the following condition, does the shadow form?
A. When the object lies behind the screen
B. When there is source of light and an object but no screen.
C. When screen is between the object and the source of light.
D. When the object lies between the source of light and screen.
6.3 when does the lunar eclipse occur?
A. When the moon comes between the sun and the earth.
B. When the sun comes between the Earth and the moon
C. On full moon day and during night time, when three heavenly bodies comes in a straight line.
D. None of these.
6.4 the object that does not give out light on its own is the:
A. Star
B. Lighted matchstick
C. Light bulb
D. Shining mirror
6.5 which of the following material allows light to pass through it?
A. Copper
B. Rubber
C. Water
D.wood
Q7. Write true or false. Rewrite the false statement.
7.1 light does not always travel in straight line.
7.2 A shadow always resembles the shape and size of the object.
7.3 if the shadow of earth falls on the moon, the eclipseis called solar eclipse.
7.4 the image in a pinhole camera gets blurred if the hole is made smaller.
7.5 we cannot see an object through a transparent medium.
Q1. Who and when discovered that current carrying wires creates a magnetic field around it?
Q2. Distinguish between a natural and artificial magnet. Write 4 points.
Q3. Explain magnetic induction method with the help of suitable example.
Q4. Which one among the following is odd:
A. Aluminium
B. Bismuth
C. Silver
D. Cobalt
Q5. What do you mean by pole of a magnet? Where it is located in a magnet?
Q6. Draw a diagram to show that a magnet has a magnetic field around it.
Q7.why care is taken not to leave a magnet all alone?
Q8. Write five uses of a magnet.
Q9. Differentiate between a bar magnet and electromagnet. Write 5 points.
Q10. A ........... Current produces a magnetic field around it.
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. No, it is not possible to measure height of a person by using 1 kg of mass because height is a different physical quantity than the mass. And we also know that kg is the SI unit of mass where as the SI unit of length is metre. In order to measure height of a person we should use metre only.
2. A metre ruler can be used to measure the thickness of a coin even if it is less than 1 mm. For this the height of a stack of few number of coins Say 10 coin, is measured by using the metre rule and then the thickness of a coin is obtained by dividing the height with the number of coins in the stack.
3. To express the area of a big agricultural field or a city, we use the bigger units of area called the decametre² (are),hectare and km².
1 decametre² = 1dam × 1 dam
= 10 m × 10 m
= 100 m²
= 10² m²
1 hectare = 100 m × 100 m
= 10000 m²
= 10⁴ m²
1 kilometre² = 1 km × 1 km
= 1 × 10³ m × 1× 10³ m
= 10³ m × 10³ m
= 10⁶ m²
= 1000000 m².
4. Area of a big rectangular field can be measured by using formula method. If length and breadth of a rectangular field is given then we can use the formula as
Area of a rectangular field= length × breadth.
Area of a leaf can be calculated by using graphical method. Place the given leaf on a graph paper. Draw its outline on the paper and remove it. Count the number of complete square. 10 had the number of incomplete squares which are half or more than half within the outline. Ignore the square which are less than half within the outline. This number one x the area of one square gives the approximate area of the given leave.
Area = (number of complete square + number of half or more than half of incomplete square) ×area of 1 square.
By using graphical method we can find approximate area of any irregular shape body. Whereas area of any regular shape body can be formed by using formula method.
5. 1 clinical Thermometer is used by doctors to measure the temperature of a patient where as laboratory thermometer is used in physics lab to measure temperature of a body for experiment purpose.
2. Range of clinical thermometer is from 35 degree celsius to 42 degree Celsius whereas the range of laboratory thermometer is from -10 degree Celsius to 110 degree Celsius.
3. Clinical thermometer is used to measure very small temperature where as laboratory thermometer is used to measure temperature of ice to boiling water .
6. 1. Those Physical quantities which are not dependentor related among themselves are called fundamental quantities. Whereas derived quantities are those physical quantities which depends on fundamental quantities.
2. Some examples of fundamental quantities are length ,mass ,time ,temperature ,current, amount of substance etc. Whereas area ,volume ,speed ,density , acceleration are some examples of derived quantities.
7. Mass can be defined as amount of substance contained or present in a body.
Or
The mass of the body is the quantity of matter contained in it.
The SI unit of mass is kg.
Definition- in 1889 1 kg was defined as the mass of a cylinder of platinum iridium alloy kept at the International Bureau of weights and measures at serves near Paris.
Or
The mass of one litre of water at 4 degree celsius is taken as 1 kg.
8. 5days 5minutes 5 seconds= 5×24hr +5×60s +5s
= 5×24×1hr + 300s + 5s
=5×24×60minutes + 305 s
=5×24×60×1minute + 305 s
=5×24×60×60s + 305s
= 120×3600 s + 305 s
= 422000 s + 305s
=422305 s.
1. A molecule is very small in size.The Range molecules is between 10-⁹ m to 10-¹⁰m.
2. There are three states of matteri.e., solid,liquid & gases.Ammonia belongs to gaseous state.
3. The molecules of liquid and gas move in zigzag direction continuously within the boundary surface of the container or vessel in which they are kept, in all possible directions at all possible speed .They are in astate of incessant random motion.
4. Thermal expansion takes place in all three States of matter. Thermal expansion is least in solid and most in gaseous state whereas in liquid it is in between solid and gaseous state.
5. Maharishi Kannad was an Indian philosopher. He was the first to suggest that all forms of matter are composed of extremely small particles known as Anu and that each Anu may be made up of still smaller particles called Parmanu.
6. A molecule or a cluster of several molecules is called a nanoparticle. It is equal to 10-⁹ m.
7. A rigid body is a body whose shape and size remains same irrespective of the the force applied on to it. Example a metal ball is a rigid body for small magnitude of force. But if force is increased and shape of a metal ball is changed then it cannot be said to be a rigid body.
8. The change in state of matter of a substance from a solid to liquid or from liquid to gas is brought about by imparting heat energy to it at a constant temperature. The constant temperature at which a solid substance melt into liquid state by absorbing heat energy is called as melting point.
The constant temperature at which a liquid changes into gaseous state by absorbing heat energy from the surrounding is called as boiling point of that substance.
9. Sublimation is a process in which a solid substance directly changes into gaseous state by absorbing heat energy from surrounding.eg. camphor,napthlene ball,ammonium chloride etc., .
Condensation is a process in which a gaseous substance Changes into liquid state by releasing heat energy to the surrounding.eg during rainfall water vapours of cloud gets converted rain water.
10. The force of attraction between the particles of two different substances is called the force of adhesion or adhesive force. While pasting a substance by using Fevicol , there are two different substances. So,There will be a force of adhesion between them.
1. What do you what do main by the poles of a magnet? Where are the poles of a bar magnet located?
2. Can we magnetize A copper bar? Give reasons for your answer.
3. Is it possible for us to isolate one pole of a magnet? Explain it.
4. Sudipto's mother was arranging her stitching box. Suddenly, the stitching box slipped from her hand and all the needles in the box got scattered on the ground. How can we collect all the little without wasting much of our time?
5. What do you mean by demagnetization? What are the various ways in which magnets can lose their magnetism?
6. Ritwik is seated in a room in which that sunlight is unavailable. He is is asked to sit facing East. Name a single compact device that he can use to fulfill this requirement. Suggest the sequence of step that he needs to follow.
7. Abhishek had two identical iron pieces X and Y, onely e one of which is a magnet. How he can find that which one is a magnet without using anything ?else.
8. Can we magnetise an iron piece permanently by the method of magnetic induction? Justify your answer.
9. Why we should take care of a magnet? How we can take care of a magnet? explain it.
10. A.Distinguish between natural magnet and artificial magnet.
B.write four differences between a permanent magnet and an electromagnet.
1. we often see bright circular patches of light on the ground under a tree on a sunny day.expain it.
2.what inference do you get from the fact that when an object is placed in the path of light a shadow is formed behind the object?
3. The image formed in a pinhole camera is inverted. why.Explain it.
4. Write any two observations from everyday life which show that light travel in a straight line.
5. Explain why we are able to to see the table and chair in a room during daytime?
6. Classify the given objects into Luminous and non luminous objects:
Meteor,planets,mirror,firefly,electric bulb,moon,chair,star,jelly fish,match stick.
7. Explain the type of shadow we expect to get when we have an Opaque object before a source of light very much bigger than the object with the help of suitable diagram.
8. We do not see any Shadow of a bird flying high up in the sky. Why? Explain it with the help of a suitable ray diagram.
9. When an apple is put in front of a small lighted up bulb, the shadow of the Apple appears on a plain white sheet kept behind the Apple. What according to you are the likely changes in the appearance of the shadow as the paper sheet is gradually moved farther and farther away from the combination of the the bulb and the Apple. Give the reason for your answer.
10. Explain why lunar eclipse takes place only on full moon day?
1. Is there any multiplication of force in a single fixed pulley? why is it considered a machine?
2. State the principle of lever in terms of mechanical advantage. How will you to write the principle of a lever in terms of effort arm & load arm?
3. The load arm in a crow bar is 3/5 of the effort arm. Find the load that can be lifted by using this crow bar by applying an effort of 3 Newton.
4. A Boy can apply a maximum effort of 5 Newton. Find the load that he can lift using a crowbar of length 4 m whose fulcrum is at a distance of 2 m from the point of application of the effort.
5. The rod of a lemon cutter is 40 cm long. The lemon,requires force of 9 Newton for its cutting, is kept at a distance of 10 cm from its fulcrum end. Find the effort needed?
6. The the fulcrum of a crowbar is at a distance of 50 cm from the load. If the the total length of the crowbar is 300 cm, how much load can it lift by applying and effort of 400 Newton?
7. A rod whose length is is 1.40 m has its fulcrum situated at a distance of 0.2 m from the load . Calculate the mechanical advantage of the rod.
8. A wheelbarrow has an effort arm 160 cm long and a load arm 40 cm long. What is its mechanical advantage?
9. Is it possible to increase the mechanical advantage of a lever. Justify your Answer with the help of a suitable example.
10. Why roads on Hills are made to have very gentle slopes?
1. Define 5kgf.
2. What do you understand by the term 'net force ' acting on a body is zero.explain it with the help of suitable example.
3. A boy says that weight of his father is 85Kgf. Is this statement correct?comment on to it.
4. Explain the principle on which a spring balance works.
5. Distinguish between contact force and non contact force with the help of suitable example.
6. Explain balanced force and unbalanced force with the help of suitable example.
7. Distinguish between gravitational force and magnetic force.
8. Define friction. Write four effects of friction.
9.Why Vehicles like cars ,trucks, scooters, bicycles and luggage trolleys etc., are provided with wheels?
10.Is Friction force always disadvantages for us? Explain it with 3 examples.
1. Is it possible to measure height of a person by using 1 kg.Justify your answer.
2. How will you measure thickness of a coin by using a metre ruler ?explain.
3. Name some units by which we can measure area of a playground large agricultural fields and so on. How are they related to each other.
4. Explain how will you measure area of a a leaf and a rectangular field whose dimension is given to you.
5. Distinguish between laboratory thermometer and clinical thermometer . Write three differences.
6. Distinguish between fundamental units and derived units of a physical quantities with suitable examples.
7. Define mass and explain devices which are used to measure very small masses accurately.
8. Convert 5 days 5 minutes 5 seconds into SI unit of time.
9. Diameter of a circular playground is equal to 98m. Find the area and circumference of the playground.
10. Convert the following into Si units
A. 0.0067km = ...........
B.3000feet =.......
C. 5908 pound =.........
D. 457hours =........
1. A molecule is very small in size. What is the range of molecules size?
2.Ammonia belongs to which state of matter?
3. What do you mean by incessant random motion of a molecule?
4. Liquids have high thermal expansion. What does it mean?
5 explain Maharishi Kannada's view on composition of matter.
6.Define a nanopatticle.
7. What do you mean by a rigid body.
8. What do you mean by change in state of a matter?
9. Distinguish between fusion and vaporization.
10. Mica sheet is pasted on a wooden table by using Fevicol. Explain the force of attraction on the basis of your physics textbook ?
1.Resultant force always acts in the direction of
Ans. Greater force.
2.An example of contact force is
Ans. Friction or frictional force.
3.The force which always causes attraction is
Ans. Gravitational force
4.Gravitational unit of force is
Ans. Kilogram force.
5.In pulling a cart, the force applied by a horse is
Ans. Muscular force.
6.Tyres of of vehicle have grooves on them for
Ans. Increasing friction.
7.Electro static force is
Ans. Both attractive as well as repulsive.
8.Which one of these is not used to increase the friction
Ans. Polishing.
9.Frictional force increases with increase in
Ans. Roughness of surface.
10.1 kilogram force is equal to
Ans. 9.8N
11.Ball bearing is used to
Ans. To decrease friction.
12.The pull of of Earth is
Ans. Gravitational force.
13 .Which of the following are contact forces
Ans. All of these (muscular force, mechanical force, frictional force)
14. Spring balance is used to measure
Ans. Weight.
15.S.I. unit of of force is
Ans. Newton.
16.
A) force - push or pull
B) friction- consequential force
C) cause of friction- roughness
D) advantages of friction- writing on a paper
E) force of gravity- weight of a body
1.A force of 10 Newton acts on a body in the upward direction and a force of 12 Newton acts on it in the downward direction .find the resultant of the forces acting on the body?
Ans. A force of 10 Newton acts on a body in the upward direction and a force of 12 Newton acts on it in the downward direction.
So, 12N - 10N = 2N in downward direction.
2.Two forces of 9 Newton and 7 Newton acts on a body to the left while another force of 16 Newton acts on it to the right .find the resultant of the forces?
Ans.9N + 7N = 16 N acts to the left side.
16N = 16 N acts to the right side.
Resultant force is zero.
3.A body is moving downwards. Forces of 20 Newton and 20 Newton act on it upwards, forces of 25 Newton and 20 Newton act on it downwards. Will its peed
Ans.20 N + 20N = 40N acts upwards.
25N + 20 N = 45N acts downwards
4.Which of the following is a contact force?
Ans. Tension force.
5.A charged comb picks of bits of paper because of
Ans. Electrostatic force.
6.In which of the following cases is friction a disadvantages to us
Ans.Parts of a machine rubbing against each other.
7.Which of the following increases friction
Ans.treads on a tyre
8.A Boat is streamlined to reduce the resistance to motion offered
Ans. By water.
9.The friction does not depends on
Ans . Mass of the body.
10.The shape of a car is streamlined to decrease friction with
Ans . Air
11.The non contact forces in magnitude depend on the distance of separation. When distance of separation is doubled the magnitude of force becomes
Ans( 1/4) th of initial force
12.Which of the following statement is incorrect
Ans.The unit of weight is kilogram.
13.Friction is not decreased if
Ans.the surfaces are made dry
14.An Apple falls downward because of
Ans.None of these.
15.A force to be expressed correctly requires
Ans.Both the magnitude and direction
16.A Force does not change
Ans.Mass of the body.
17.The frictional force acts in the direction of
Ans.Opposite to the motion of the body.
18.Friction is reduced by
Ans.Making the surfaces wet.
19.Which one among the following option is odd one:
Ans.Gravitational force.
20.A body needs a force X just to start motion on a surface a force Y to continue its motion and a force Z to roll on the surface then
Ans. Y>Z
*Measurement of time-
-time-the interval between two instances or events is called time.
-SI unit of time is second.
-symbol is s.
-def.
1 second is defined as 1/86400 part of a mean solar day.
Bigger unit of time:
1 minute=60 seconds
1hour=60 minutes
=60×1 minute
=60×60s
=3600 s
1 day=24×1 hour
=24×3600 s
=86400 s
1year=365×1day
= 365× 86400s
=31536000s
≈3.15×10⁷ s
*Devices for measuring time:
1. A pendulum clock-
Time is measured by making use of the time taken by a pendulum to complete one oscillation.
-oscillation-one complete to and fro motion of a pendulum is known as one oscillation.
-time period-time taken by a pendulum to complete its one oscillation is called as it's time period.
-the time period of a seconds pendulum is 2 second.
-•The seconds arm moves by one small division when the pendulum moves from one extreme to the other extreme.i.e., 1s
•the minutes are moves by a small division and the seconds arm completes one round.i.e., 60s
•the hours arm moves by 5 small divisions when the minutes arm complete one round.i.e.,1 h.
2.A watch-
-the seconds arm is driven by a wound up spring.
Measuring devices for short time interval:
1. Stop clock
2. Stopwatch
•they have arrangements to start, to stop and to reset at zero.
•electronic stopwatch-
-electronic stopwatch can measure time intervals accurately upto 0.01 seconds.
-electronic stopwatch is used for measuring the timings of athletic activities.
*Measurement of temperature:
-the temperature is the measure of degree of hotness or coldness of an object.
-SI unit of temperature is Kelvin.
-symbol is K.
-ice point is 273.15 K
-steam point is 373.15 K
-the number of divisions between ice point and steam point are 100.
-some other units of temperature are:
1.Degree Celsius
-symbol is °C
•given by scientist Andrews Celsius.
- it is used to measure days maximum & minimum temperature.
- ice point is zero degree celsius.
-steam point is 100 degree Celsius.
-the number of divisions between ice point and steam point are 100.
•one degree on Celsius scale is equal to 1.8 degree on fahrenheit scale.
•degrees celsius also called as centigrade scale because it has 100 divisions between the ice point and steam point in the Celsius scale.
2. Degree fahrenheit
-symbol is °F.
•named after the scientist G.D. Fahrenheit
- it is used to measure body temperature of a person.
- Normal body temperature = 98.6°F
-ice point is 32 degree fahrenheit.
-steam point is 212 degree fahrenheit.
-the number of divisions between steam point and ice point are 180.
*Relationship between three temperature scales:
(Symbol -ice point)/ number of divisions
(°C - 0 )/100 = (°F - 32)/180 = (K- 273.15)/100
(°C - 0 )/5 = ( °F - 33 )/18 = (K- 273.15 )/5
Relationship between degree Celsius and degree fahrenheit scales:
(°C - 0 )/5 = (°F - 32)/18
⇒ (°C ) = 5×( °F - 32 )/18
(°F- 32)/18 = °C/5
⇒(°F - 32) =18×°C/5
⇒°F = 18×°C/5 + 32
Relationship between degree Celsius and Kelvin:
(°C - 0 ) = ( K - 273.15)
⇒ ° C = 5 × (K- 273.15)/5
(K - 273.15)/5 = ( °C - 0)/5
⇒ ( K - 273.15) = 5 × ° C/5
⇒ K = 5 × °C/5 + 273.15
Relationship between degree Fahrenheit and Kelvin scale:
(°F - 32)/9 = ( K - 273.15)/5
⇒(°F - 32) = 9× (K - 273.15)/5
⇒°F = 9× (K- 273.15)/5 + 32
(K - 273.15)/5 = ( °F - 32)/9
⇒(K - 273.15) = 5 × (° F - 32)/9
⇒K = 5×( °F - 32)/9 + 273.15
*Device used to measure the temperature of an object:
-temperature is measured by device called thermometer.
1. Laboratory thermometer:
_description-
-glass capillary tube with a bulb at one end.
-the bulb filled with Mercury.
-the system has markings from - 10°C to 110°C.
| •range of a laboratory thermometer=upper fixed point - lower fixed point |
= 110°C - (-10°C)
= 110°C + 10°C
= 120°C
•it is used in labs for measuring temperature during experiments, Daily maximum- minimum temperature of the day etc.,
2. Clinical thermometer:
-doctors use special thermometer called the clinical thermometer for measuring the temperature of the patient's body.
•description:
-it has markings from 35 degree celsius to 42 degree Celsius.
-slight bend or king in the stem just above the bulb called as constriction to prevent the Mercury from falling back all by itself.
-red arrow on it indicates the normal temperature of a person= 37°C or 98.6°F
-clinical thermometers marked in °F have markings from 95°F to 110°F.
Measuring the temperature of a patient's body with clinical thermometer:
-1. Clinical thermometer is slightly jerked to bring the level of Mercury in its capillary tube below the mark 37 °C.
2.thermometer bulb is kept below the tongue or under the arms pit of the patient for about a minute.
3. It is taken out and reading is noted.
4. If the reading is more than or less than 37°C,then then person is abnormal or suffering from some illness.
*clinical thermometer cannot measure the temperature of boiling water because it can measure only up to 42 degree Celsius where as the temperature of boiling water is hundred degree Celsius.
•digital thermometers are preferred instead of Mercury thermometer . Because mercury is highly toxic for human beings.
*Physical quantities:
-whether a physical quantity depends on each other or not it can be divided into two :
1. Fundamental quantities:
-a physical quantity which does not depend or related to other physical quantities are called as fundamental quantities. Example length, mass, time, temperature etc.,
2. Derived quantities:
-physical quantities which are expressed in terms of the other measurable fundamental quantities like length, mass, time, etc., are called derived quantities. Example area, volume, speed, density, force, weight,etc.,
-area= length×breadth
- volume= length×breadth×height
-speed= distance/time.
*Measurement of area:
-area-the total surface occupied by an object is called its surface area or simply the area.
-it can be expressed in terms of the product of two measurements in length.
-SI unit is m²
-CGS unit is cm²
-area of regular shapes-(formula method)
1. Area of square=l×l
2. Area of a rectangle= l× b
3. Area of a triangle=1/2 × base×height.
4. Area of a circular lamina of radius r
=πr², π =22/7 or π=3.14
•area of irregular surfaces (By graphical method)
-the area of regular or irregular surface can be obtained by using a graph paper.
Procedure:
1. Place the given surface on a graph paper.
2. Count the number of complete squares.
3.Add the number of incomplete squares recharge half or more than half within the outline.
4. Area of one box is 1 cm square.
More than half boxers •
Approximate area=(number ofcomplete squares +number of half hour more than half of incomplete square)×area of one square
Multiple and submultiple units of area:
-the area of a big agricultural field or a city are measured by using bigger units of area such as decameter square (are), hectare, square kilometre etc.,
1 decameter ² =100m²
1 hectare=100m× 100m
= 10000m²
=10⁴m²
1km²= 1km×1km
=1000m×1000m
=10⁶m²
1km²= 100 hectare.
1dm²= 10cm×10cm
=100cm²
=10²cm²
1cm²= 1/100 m × 1/100 m
= 1/10000 m²
= 1/10⁴ m²
=10-⁴ m²
1mm²= 1mm × 1 mm
= 10-⁶ m²
1yard²=0.836m²
1ft²=0.09290 m²
1acre=4046.856m²
*Physical quantities-
-A quantity thú㎲at can be measured is called a physical quantity.
-example mass, length, time, temperature, area, volume, force, weight, displacement, velocity, etc.
-physical quantity can be divided into two types:
•scalar quantity-a physical quantity which can be expressed only in terms of magnitude.
•example mass, length, time, temperature, area, volume etc.
•vector quantity- a physical quantity which requires the magnitude as well as the direction to express them..
•eg, force, weight, displacement, velocity etc.,
Physical quantity=magnitude×unit
= n×u
*Measurement-
-measurement is a comparison of an unknown quantity with a known fixed quantity of the same kind.
-measurement is basically a process of comparison.
-unit-unit is the quantity of a constant magnitude which is used to measure the magnitude of other quantities of the same nature.
- magnitude- numerical value.
- eg. Mass of a man=65 kg
65 is a numerical value called as magnitude.
Kg is the unit of mass.
-eg height of a man=1.65m
1.65 is a numerical value called magnitude.
m is the unit of height.
-measurement is expressed as:
Measurement=n×u
n= magnitude
u= unit
*Choice of unit:
1. It should be of convenient size.
2. It must be universally accepted.
*System of units:
1. CGS system/British system of unit-
Length- centimetre- cm
Mass -kilogram- kg
Time - second - s
2. FPS system/French system of unit-
Length-foot- ft
Mass - pound - lb
Time - second - s
3. MKS system/metric system of unit-
Length- metre- m
Mass- kilogram- kg
Time- second- s
*SI system of units-
In 1960, the scientist accepted a set of units for measuring the basic physical quantities length, mass, time and temperature to be called as standard international units inshort si units.
Length-metre- m
Mass-kilogram- kg
Time- second- s
Temperature- Kelvin- K
Luminous intensity-candela-cd
Electric current- ampere- A
Amount of substance- mole- mol
Complementary fundamental units:
Angle- radian- rd
Solid angle- steradian- st-rd
Multiples are used to measure a large quantity/prefixes used for big measurements.
deca 10¹ da
hecto 10² h
kilo 10³ k
mega 10⁶ M
Giga 10⁹ G
tera 10¹² T
peta 10¹⁵ P
Submultiples are used for small measurements.
deci 10-¹ d
centi 10-² c
milli 10-³ m
micro 10-⁶ μ
21. Draw diagrams to illustrate the positions of fulcrum load and effort in each of the following:
a) see-saw - figure 4.8 a.
b) beam balance-figure 4.8 d
c) a nutcracker -figure 4 .10 a
d) a pair of forceps- figure 4.12 d
22. How can you increase the mechanical advantage of a lever?
Ans. Mechanical advantage of a lever can be increased in following ways:
a) by increasing the effort arm and decreasing load arm.
b) by reducing the friction at the fulcrum of a lever.
23. How does the friction of the forum affect the mechanical advantage of the lever?
Ans. The friction at the fulcrum, increases the mechanical advantage of the lever.
24. State three differences between three classes of the levers.
Ans.write from page no.55. distinction between the three classes of levers.
25. What is a pulley?
Ans.a pulley is a simple machine which is used for raising a load up by applying the effort downwards.
26. What is the mechanical advantage of an ideal pulley?
Ans. The mechanical advantage of an ideal pulley is 1 or 100%.
27. The mechanical advantage of an actual pulley is less than 1. Give reason. What is a justification for using the pulley then??
Ans. The mechanical advantage of an actual pulley is less than 1. The reason for less than one is is because of friction between the rope and the pulley.
pulley is not used as a force multiplier but it is used for changing the direction of the effort. To apply I the effort in a more convenient direction that is in downward direction.
28. Draw a neat labelled diagram showing a pulley being used to lift a load. How are load and effort related in an ideal situation?
Ans. Figure 4.14 of your physics book.
In an ideal situation, effort is equal to load.
29. What is an inclined plane? What is its mechanical advantage? Give two examples where it is used.
Ans. An inclined plane is a simple machine which is used to move a load up with a less effort. It is a sloping or slanting surface.
The mechanical advantage of an inclined plane is always greater than 1.
Two examples of incline plane are as follows:
a) the staircase in our house.
b) the roads on a hill are made in inclined with a small slope.
30. What is a screw? Give two examples.
Ans. Screw is a simple machine which appears like an incline plane wound around a rod with a pointed tip. It is a modified form of an inclined plane.
Following are the two examples of A screw:
a) screw is used to fix a door through hinge.
b) screw Jack is a simple machine which is used to lift heavy vehicles such as car, trucks, buses etc.
31. What is wheel and axle? Give two examples.
Ans.the wheel and axle is a simple machine having a wheel and an axle. the linear motion of axle is obtained by rotating the wheel so as to reduce friction.
Following are the two examples of wheel and axle:
a) steering wheel
b) screw driver.
32. How does a wheel help in moving the axle?
Ans.A wheel help in moving the axlel by reducing the frictional force.Because rolling friction is less than the sliding friction.
33. What is a wedge? Give two examples.
Ans. A wedge is a sharp edge formed by joining two inclined planes together to form a sharp edge which is used to split a log.
The two examples of a of a wedge are:
a) nail\knife
b) needle\axe.
34. Name the machine to which the following belong:
a) beam balance-class 1 lever
b) lemon crusher- class 2 lever
c) sugar tong- class 3 lever
d) ramp- an inclined plane
E) door knob- wheel and axle
f) needle- wedge
35. What care would you take to increase the lifespan of a machine which you use?
Ans. Following cares we should take to increase the lifespan of a machine:
a) machine machine should be kept clean and free from dust particles.
b) it should be prevented from getting rusted. By painting it with paint from time to time.
c) to reduce friction of the moving parts of a machine, moving parts must be properly lubricated from time to time.
36. Select the correct statement:
a) A wheel barrow is a lever of class 1.
b) the efficiency of a machine is always 100%.
c) friction in moving parts of a machine reduces its efficiency.
d) no lever has the mechanical advantage greater than 1.
e)it is easier to lift a load vertically up then to push it along an inclined plane.
f) screw is made by two inclined planes placed together.
Ans.c) friction in moving parts of a machine reduces its efficiency.
13. What is a lever?
Ans. A lever is a rigid bar either straight or bent which can turn about a fixed point called the fulcrum.
14. Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load and effort in each kind of lever.
Ans. A lever can be of three types that is class 1 lever, class 2 lever and class 3 lever.
Class 1 lever-
*the levers in which the fulcrum is in between the load and the effort are called the levers of class 1. Draw figure 4.7 from your physics book.
*the mechanical advantage of levers of class 1 can be greater than 1, equal to 1 or less than one.
*Example seesaw, a pair of scissors, beam balance, a pair of pliers etc.
Class 2 lever-
*the levers in which the load is in between the pulchrum and the effort are called the levers of class 2. Draw figure 4.9 from your physics book.
*The mechanical advantage of class 2 levers is always more than 1.
*Examples of class two levers are are nutcracker, wheelbarrow, paper cutter, lemon squeezer etc.
Class 3 levers-
*the levers in which the effort is in between the welcome and the load are called the levers of class 3. Draw figure 4.11 from your physics book.
*The mechanical advantage of class 3 levers is always less than 1.
*Examples of class 3 levers are are a pair of tongs, sugar tongs, knife, spade for lifting soil or coal etc.
15.what do you mean by the mechanical advantage of a lever?
Ans.the mechanical advantage of a lever is equal to the ratio of the effort arm to the load arm.
Mechanical advantage= load/effort.
Or
Mechanical advantage=effort arm/load arm.
It gives us an idea that how many times our efforts get multiplied by the machine.
16. Which class of lever has the mechanical advantage always more than one? Give an example.
Ans. Class 2 lever is a example where mechanical advantage is always more than 1.
Example nutcracker, wheelbarrow, bottle opener etc.
17. Which class of lever has the mechanical advantage always less than 1? Give an example.
Ans. Class 3 lever is a lever was mechanical advantage is always less than 1. Example pair of tongs ,knife ,spade used for throwing all lifting soil etc.
18. Give one example of class one lever in each case where the mechanical an is a) more than one. b) equal to 1. C) less than 1.
Ans. A pair of plier is an example of class 1 lever where mechanical advantage is greater than 1.
Beam balance example of class 1 where mechanical advantage is equal to 1.
a pair of scissors age an example of class 1 lever where mechanical advantage is less than n1.
19. Name the class to which the following levers belong:
A. A pair of scissors -class 1 lever
B. Lemon squeezer -class 2 lever
C. A nutcracker - class 2 lever
D. A pair of sugar tongs-class 3 lever
E. a beam balance - class 1 lever
F. An oar roaming about- class 1 lever
G. a wheelbarrow - class2 lever.
H. A seesaw-class 1 lever
I. A pair of pliers-class 1 lever
J. Crowbar- class 1 lever
20 the diagram given below shows the three kinds of levers. Name the class of each lever and give one example of each class.
Ans. a) class 2 lever. Example wheelbarrow bottle opener etc.
b) class 1 lever. Example beam balance, seesaw etc.
C) class 3 lever. Speed using for throwing soil, sugar tong etc.
1. When is work said to be done by a force?
Ans. A work is said to be done by a force when a body is displaced or moves in the direction of force applied.
2. What is energy?
Ans. Energy is the capacity or ability of a body to do work.
3. What do you understand by a machine?
Ans.machine is a device which acts as a force multiplier or speed multiplier allowing us to apply effort at a more convenient point in and easier direction.
4. What is the principle on which a machine works?
Ans. No machine work of its own. When energy is supplied to it, it does some useful work. Work done on the machine is called as work input and work done by the machine is called as work output.
5. State two functions of a machine.
Ans. Two functions of a machines are as follows:
1. Acts as a force multiplier
2. Acts as a speed multiplier
6. Name six simple machines. Give an example of each machine.
Ans. Six simple machines are as follows:
1. The lever example Mango cutter, beam balance, a pair of scissors, etc.
2. The pulley eg.pulley is used in well to draw water from it,to lift heavy load in factories etc.
3. The wheel and axle example door knob, steering wheel, etc.
4. The incline plane example staircase , ramp etc.
5.The wedge example of needle,axe,etc.
6.The screw.eg. fixing hinge in door & windows,attaching lock in the door etc.
7. Define the term 'work output'and'work input'in relation to a machine.
Ans. Work output is the usefull work done by the machine on the load.
Work input is the work done on the machine by the effort.
8. Explain the term mechanical advantage of a machine.
Ans. The mechanical advantage of a machine is the ratio of the load to the effort. Or
the factor by which machine multiplies the force applied is called the mechanical advantage.
In words it can be written as,
Mechanical advantage=load/effort
1.If mechanical advantage of a machine is greater than 1 then it acts as a force multiplier.
2.if mechanical advantage of a machine is less than 1 then it acts as a speed multiplier.
3.if mechanical advantage of a machine is equal to 1 then it acts as a direction changer or to apply effort at a more convenient point in a convenient direction.
9. Define the term efficiency of a machine.
Ans.the efficiency of a machine is the ratio of the useful work done by the machine to the work you put into the machine by the effort.
Efficiency=work output on load/work input by effort.
10. What is an ideal machine?
Ans. Ideal machine is a machine in which no part of the work done on the machine is wasted. For an ideal machine, the work output is equal to the work input. The efficiency of an ideal machine is 100%.
11. Can a machine have an efficiency of 100%? Give reason to support your answer.
Ans. No .
Machinec have an efficiency of 100% because some part of the work done on a machine is always wasted in overcoming the friction between the moving parts of the machine.
12. 'A machine is 75% efficient'. What do you understand by this statement?
Ans. If a machine is 75% efficient,it means that 75% of the work input to the machine is obtained as the useful work output. The remaining 25% of the work input has been wasted in overcoming the friction.
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