Bumpers on Cars Are Not of Much Use in a Collision

Multiple Choice

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 2.0 m/s (about 4.5 mph) . (Bumpers are built with springs that compress to provide a stopping force without, hopefully, denting the metal.)

A) 1.8 × 10⁴ N
B) 1.6 × 10⁴ N
C) 5.4 × 10⁴ N
D) 6.5 × 10⁵ N
E) 3.2 × 10⁴ N