12.A car moving with a speed of 20m/s can be stopped by applying brakes, after travelling a distance of 2m.The retardation of the car is

solution:

car is moving with a speed(u)=20m/s

it can stopped by brakes ,that means final velocity (v)=0

in mean time ,it travelled a distance (S)=2m.

by given information ,initially it has initial velocity and then comes rest .so, the car is in retarded motion.

we have the formula, V²-u²=2aS

0-(20)² =2a(2)

-400=4a

a=-100m/S²

The car has retardation is a=-100m/S²