Question

find the initial velocity of a car which is stopped in 10 seconds by applying breakes . The retardation due to brakes is 2•5m/s ?

Answer 1

Let inital velocity of car = Vo
finally car comes to rest
so, final velocity ( Vf )= 0

use, kinematic equation ,
Vf = Vo + at
here, Vf = 0
a = -2.5 m/s²
t = 10 second

0 = Vo + (-2.5) × 10
Vo = 25 m/s

Answer 2

Given :
v=0. (brakes)
a= -2.5m/s². (retardation)

t= 10sec
From first equation of motion

v= u+at

0= u+ (-2.5×10)
u-25=0
u= 25 m/sec

Hence the initial velocity is 25m/sec