Question

A car is moving in a straight line with speed
18 kmh. It is stopped in 5 s by applying the brakes.
Find : (i) the speed of car in m s', (ii) the retardation
and (iii) the speed of car after 2 s of applying the
brakes.

Answer 1

Answer:i) 30m/s

ii) -6m/s sq.

iii) 18m/s

Explanation:

i) speed in m/s= 18 X 5/3

= 30m/s

ii) u=30m/s

v=0

t=5s

To find = a

Using,

v=u+ at

or, 0=30+a X 5

or, -30=5a

or, a= -30/5

or, a=-6m/s sq.

iii) time=2s

u=30m/s

a=-6m/s sq.

To find=v

Using,

v=u+at

or, v=30+(-6 )X 2

or, v=30-12

or, v=18m/s