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.
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