Question

A car takes 20s to stop after the application of breaks. What was it's initial velocity and how much distance did it cover during this interval if the brakes produced a uniform retardation of 0.6metre per second square?

Answer 1

Hi there...

initial velocity = u

final velocity = v = 0

acceleration = - 0.6 m / s^2 [ retardation ]

time = t = 20 s

by the equation of motion,

v = u + at

0 = u + (-6/10) × 20

0 = u - 12

.: u = 12 m / s^2

• INITIAL VELOCITY = 12 m / s^2

now ,

s = distance covered by the car before coming to rest

by the equation of motion ,

s = ut + 1 / 2 at^2

s = 12 × 20 + 1 / 2 × ( -0.6 ) × 20 × 20

s = 240 - 120

.: s = 120

• DISTANCE COVERED = 120 m

HOPE IT HELPS...