Acar's bumper is designed to withstand a 4.32 km/h (1.2-m/s) collision with an immovable object without damage to the body of the car. the bumper cushions the shock by absorbing the force over a distance. calculate the magnitude of the average force on a bumper that collapses 0.195 m while bringing a 910 kg car to rest from an initial speed of 1.2 m/s.

At 20∘c, the hole in an aluminum ring is 2.800 cm in diameter. you need to slip this ring over a steel shaft that has a room-temperature diameter of 2.804 cm . 1. to what common temperature should the ring and the shaft be heated so that the ring will just fit onto the shaft? coefficients of linear thermal expansion of steel and aluminum are 12×10−6 k−1 and23×10−6 k−1 respectively.