## Motion-Very Short Answer Type Questions

### Question 1. when graph is parallel to time axis, what can you say about the motion?

**Answer.**

The body remains at rest.

### Question 2. What is the value of acceleration, if *v-t *graph is a straight line parallel to the time axis?

**Answer. **

Zero, since slope is zero.

### Question 3. Under what condition, the distance covered by a particle is equal to the magnitude of

displacement of particle?

**Answer. **

This happens when the body moves with a constant velocity.

### Question 4. Is it possible that the average velocity of a particle is zero when its average speed is not

zero?

**Answer. **

This occurs when the particle returns to the starting point.

### Question 5. What is meant by a point object? Give some examples.

**Answer.**

Whenever the size of the object is much smaller than the distance it moves in a given time interval, the size of the object can be neglected. Then the object may be regarded as the point object. Examples: (i) A car covering a distance of 10 km can be treated as a point object, (ii) Earth can be regarded as a point object for studying its motion around the sun.

### Question 6. Can an object be at rest as well as in motion at the same time?

**Answer. **

Yes. An object may be at rest relative to one object and at the same time it may be in motion relative to another object.

### Question 7. Can the average speed of a moving body ever be zero?

**Answer. **

No, speed, being a scalar quantity, is always positive. So its average speed can never be zero.

### Question 8. A body is moving with a velocity of 10 m/s. If the motion is uniform, what will be the velocity after10 s?

**Answer.**

As the motion is uniform, the velocity remains equal to 10 m/s even after 10 s.

### Question 9. Define velocity. What is its SI unit?

**Answer.**

The distance traveled by a body per unit time in given direction is called its velocity. The SI unit of velocity is m/s.

### Question 10. Can the speed of a body vary if its velocity is constant?

**Answer.**

No. When the velocity of a body is constant, its speed is also constant.

### Question 11. Can a body have constant speed but variable velocity?

**Answer.**

Yes. For example, a body in uniform circular motion has constant speed but its velocity changes at every point due to the change in the. direction of motion.

### Question 12. What is the SI unit of retardation?

**Answer.**

m/s^{2}.

### Question 13. What is acceleration of a body moving with uniform velocity?

**Answer.**

Zero.

### Question 14. If the acceleration of the particle is constant in magnitude but not in direction, what type of path does the body follow?

**Answer.**

Circular path.

### Question 15. A ball is thrown up in air. What is the acceleration and velocity at the instant it reaches its highest point?

**Answer.**

Acceleration is 9.8 m/s^{2} acting downwards and velocity is zero.

### Question 16. A car travels 1 km and returns back to the same point in a different path. What is the average velocity.

**Answer.**

Zero. Since total displacement is zero.

### Question 17. Give an example of a motion in which the acceleration is in the direction of motion.

**Answer.**

When a body falls from the roof of a house, then the acceleration of the body is in the direction of motion.

### Question 18. Give an example of a motion in which the acceleration is against the direction of motion.

**Answer.**

When a body is thrown upward, then the acceleration is against the direction of motion.

### Question 19. What does the slope of a speed-time graph indicate?

**Answer.**

Acceleration

### Question 20. What do we get from the area between the speed- time graph of a body and the time-axis?

**Answer. **

Distance traveled by the body.

### Question 21. If the velocity-time graph of a body is a line parallel to the time-axis, what would be the acceleration of the body?

**Answer. **

Zero, because the body possesses uniform velocity.

### Question 22. A satellite goes round the earth in a circular orbit with constant speed. Is the motion accelerated?

**Answer.**

Yes.

### Question 23. If the displacement of a body is zero, is the distance covered by it necessarily zero?

**Answer. **

No, it is not necessary that the distance covered by a body is zero when its displacement is zero.

### Question 24. Can the displacement be greater than the distance traveled by an object?

**Answer.**

No, the displacement of an object can be either equal to or less than the distance traveled by the objects.

### Question 25. Under what condition will the distance and displacement of a moving object have the same

magnitude?

**Answer. **

When the object moves along the same straight line in the same fixed direction.