Bumpers on cars are not of much use in a collision. To see why, calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model) to a rest in 15 cm when the car had an initial speed of 2 m/s (about 4.5 mph). Bumpers are built with springs that compress to provide a stopping force without (hopefully) denting the metal.

a) 1.6 x 104 N

b) 5.4 x 104 N

c) 3.2 x 104 N

d) 6.5 x 105 N

e) 1.8 x 104 N