Question

Ram is travelling with 20m/s and stopped in 4 sec. What is his acceleration in m/s^2?

Answer 1

Explanation:

Initial velocity of car, u = 20 m/s

The final velocity will be, v= 0 as the car comes to rest after travelling distance of 40 m (which will be after application of brakes)

By third equation of motion we know,

v2 = u2 + 2 as

0 = (20)2 + 2 x a x (40)

- 80 a = 400

Thus, a = - 5 m/s2

Negative sign indicates that it is a retardation.

When same car is moving with double the velocity

Initial velocity, u = 2 x 20 =40 m/s

Thus,

0 = (40)2 x 2 x (-5) x s

10 s = 1600

s = 160 m

Hence, if the same car is travelling at double the velocity the distance travelled by it for same retardation is 160 m