Bumpers on cars are not of much use in a collision.

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 which compress to provide a stopping force without (hopefully) denting the metal a)3.3 x 10^4 Nb)6.5 x 10^4 Nc) 5.4 x 10^4 Nd) 1.6 X 10^4 Ne)1.8 x 10^4 N