Question

A car travels first 10 seconds with uniform
acceleration of 2 m/s from rest on straight road
and then travels with zero acceleration for next
10 seconds. The average speed of entire journey
is
(1) 20 m/s
• (2) 15 m/s
(3) 10 m/s
(4) 5 m/s​

Answer 1

Answer:-

(1) 20 m/s

Explanation:-

Given

A car travels first 10 seconds with uniform acceleration of 2 m/s from rest

And

After it, travels with zero acceleration for next 10 seconds.

To Find

Average speed of entire journey..

Solution:

Case 1

u = 0

t1 = 10 sec

a = 2m/s²

v1 = ??

From the 1st eq. of motion

V = u+at

V1 = 0 + 2(10)

V1 = 20 m/s

Case 2

t2 = 10 sec

a = 0 m/s²

u = 20 m/s

V2 = u+at

V2 = 20+0(10)

V2 = 20 m/s

Average speed = V1+V2/2

V(avg) = 20+20/2 = 20 m/s