Question

A 1400 kg van is traveling at 24m/s when the driver takes her foot off the gas pedal. The car eventually rolls to a stop after 225 meters. Find the force of friction acting on the van.

Answer 1

We can use the kinematics equation

v1^2-v0^2=2as

where v1=final velocity = 0 m/s

v0=initial velocity = 24 m/s

a=acceleration = to be determined

S=distance travelled during acceleration = 225 m

=>

a=(v1^2-v0^2)/(2S)

=(0^2-24^2)/(2*225)

=-576/450

=-1.28 m/s^2

So van is decelerating at 1.28 m/s^2

The frictional force is therefore

F = ma = 1400 kg * 1.28 m/s^2 = 1792 N