Question

when brakes are applied to a car it retarded uniformly at 5 M / S 2 and stopped after 15 seconds find the initial velocity of the car

Answer 1

retardation = - 5 m/s²
time = 15 sec
use kinematics formula,
V = U + at
where V is final velocity , U is initial velocity , a is acceleration and t is time .
here V = 0
U =?
a = -5 m/s²
t = 15 sec

then,

0 = U -5× 15
U = 75 m/s²

Answer 2

Hi there !!

Here

acceleration, a = -5 m/s²

time , t = 15 sec

Initial velocity = u

Final velocity , v = 0

v = u +at

0 = u + - 5 × 15

0 = u + (-75)

Hence .

u = 75 m/s