Question

A 1100 kg car coasts on a horizontal road with a speed of 19 m/s. After crossing a an unpaved, sandy stretch of road 32 m long, its speed decreases to 12 m/s. (a) Was the net force done on the car positive, negative, or zero? Explain (b) Find the magnitude of the average net force on the car in the sandy section.

Answer 1

Equations:

Change in kinetic energy = 1/2m(Vf^2-Vi^2) = Net (total) Work done on the object = F*d

m = 1100 kg
Vi = 19 m/s
Vf = 12 m/s
d = 32m

Calculations:

1/2(1100)(12^2-19^2) = F(net)*32
=119350/32
b) =3730 N

a) ΔEK is negative, meaning that W < 0 meaning that theta > 90 degrees (cos180 for this question)