# NCERT Class-9 Science Solutions: Chapter 8-Motion Part 4

Question 17:

The velocity-time graph (Fig.) shows the motion of a cyclist. Find

1. Its acceleration

2. Its velocity and

3. The distance covered by the cyclist in 15 seconds.

1. Since velocity is not changing, acceleration is equal to zero.

3. Distance covered in

Question 18:

Draw a velocity versus time graph of a stone thrown vertically upwards and then coming downwards after attaining the maximum height.

Question 19:

An object is dropped from rest at a height of and simultaneously another object is dropped from rest at a height. What is the difference in their heights after if both the objects drop with same accelerations? How does the difference in heights vary with time?

Initial difference in height

Distance travelled by first body in 2 s

Distance travelled by another body in 2 s

After 2 s, height at which the first body will be

After 2 s, height at which the second body will be

Thus, after 2 s, difference in height

Initial difference in height

Thus, difference in height does not vary with time.

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