Question

Find the initial velocity of a car ,which is stopped in 20 seconds by applying brakes the retardation due to brakes is 4.5 metre per second square?

90 m/s

14 m/s

60 m/s

100 m/s​

Answer 1

I hope it helps you my friend

Answer 2

Given :-

Time = 20 seconds

Acceleration = 4.5 m/s²

Final velocity = 0 m/s (As it stops)

To Find :-

Initial velocity

Solution :-

We know that

v = u + at

Where

v = final velocity

u = initial velocity

a = acceleration

t = time

0 = u + (-4.5)(20)

0 = u + (-90)

0 - u = -90

- u = -90

u = 90

Therefore

Initial velocity is 90 m/s

Know More :-

Equations of motion

v = u + at

s = ut + 1/2 × at²

v² - u² = 2as

Where

v = final velocity

u = initial velocity

a = acceleration

t = time

s = distance