Question

When brakes are applied to a uniform velocity of 72km/hr it comes to a stop after covering a distance of 50m determine retardation of the car and the time taken by it to stop

Answer 1

U=initial speed=72km/h=20 m/sec.

v=final speed  =0 km/h

time=t= 5 sec.

v=u+at

v-u=at= v-u/t=a

-20/5= -4 m/sec^2 = deacceleration

now using the eqn:-

S=ut+1/2 a

S=20*5 +  (-4) * 5*5

S=100 - 50 =50 m.