Problem 78.

A man is driving at the speed 40 mph when he see an obstacle at distance 300 ft ahead of his position. The driver applies the brakes and decelerates at How long does it take him to stop the vehicle? How far from the obstacle will the driver be when he finally stops?

Solution:

At first we need to convert all the variables into correct units (SI units):

Then we have motion with constant deceleration. Then

The car stops when then

And

The traveled distance is

Then the distance between the car and the obstacle is