Question

A car starts from rest and accelerates from rest uniformly for 10 s to a velocity of 36 kmhr^-1. It then runs at a constant velocity and is finally brought to rest in 50 m with uniform retardation. If the total distance covered by the car is 500 m, find

1. acceleration and

2. retardation.

Answer 1

1. Initial velocity of the car u = 0;

Final velocity v = 36 kmhr^-1

= (36 x 1000)/3600 = ms^-1

= 10 ms^-1

time taken t = 10 s

∴ acceleration a = (v - u)/t = (10 - 0)/10 = 1ms^-2

2. To find the retardation

During the motion with retardation, Initial velocity of the car u = 10 ms^-1

Final velocity v = 0, distance travelled, s = 50 m

Using the relation v² = u² + 2as,

0 = 10² – 2a × 50

a = (-100/(2 x 50)) = -1 ms^-2