NCERT Class9 Science Solutions: Chapter 8Motion Part 4
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Question 17:
The velocitytime graph (Fig.) shows the motion of a cyclist. Find

Its acceleration

Its velocity and

The distance covered by the cyclist in 15 seconds.
Answer:

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

Reading the graph,

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.
Answer:
Long Answer Questions
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?
Answer:
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.