Question

A motor car is at rest and acceleratesuniformly for 10 sec to a velocity of 20m/s he then runs at a constant speed and then finally brought to rest in 40mwith a constant acceleration total distance civered is 640m find the value od acceration retardation

Answer 1

HELLO THERE!

Given: A motor car starts from rest, hence u = 0.

It accelerates uniformly for 10 seconds, to a velocity of 20 m/s, so time t = 10s and v (final velocity) = 20 m/s.

From the relation v = u + at,

We have: 20 = 0 + a x 10

or a = 20/10 m/s² = 2m/s²

Finally, it is brought to rest from a velocity of 20m/s, by covering a distance of 40m. Hence in this case, u = 20m/s, v = 0.

From relation v² = u² + 2aS,

We have 0 = (20)² - 2a x 40 (since a = -a {retardation})

or 80a = 400

or a = 5m/s²

Hence your required answer is:

Acceleration = 2m/s²

Retardation = 5m/s²

THANKS!