A 2.10 X 10^3 kg car starts from rest at the top of a 5.0

mlong driveway that is sloped at 20 degrees with the horizontal.

Ifan average friction force of 4.0 X 10^3 N impedes the motion,

findthe speed of the car at the bottom of the driveway.

3.80 m/s

Explanation:

Solution: From the question we have:

A 2.10 x 10^3 kg car starts from rest at the top of a 5.0 m long driveway that is sloped at 20 degrees with the horizontal.

average friction force of 4.0 x 10^3 N impedes the motion

To find out: find the speed of the car at the bottom of the driveway.

=>h = 5*sin20 = 1.71 m.

PE = mgh = 2100*9.8*1.71 = 35,192 J.

KE = PE-work done by frictional force

KE=PE-4000*5

0.5mV^2 = 35192 - 4000*5

1050V^2 = 15,192

V^2 = 14.47

V = 3.80 m/s.