# NCERT Class-9 Science Solutions: Chapter 8-Motion Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 20:

An object starting from rest travels in first and in next . What will be the velocity after from the start?

Since acceleration is the same, we have

Question 21:

Using following data, draw time - displacement graph for a moving object:

 Time (s) 0 2 4 6 8 10 12 14 16 Displacement (m) 0 2 4 4 4 6 4 2 0

Use this graph to find average velocity for first , for next and for last .

Average velocity for first 4 s.

For next 4 s

(or as x remains the same from 4 to 8 seconds, velocity is zero)

For last 6 s

Question 22:

An electron moving with a velocity of enters into a uniform electric field and acquires a uniform acceleration of in the direction of its initial motion.

1. Calculate the time in which the electron would acquire a velocity double of its initial velocity.
2. How much distance the electron would cover in this time?