Question

Most of us know intuitively that in a head-on collision between a large dump truck and a subcompact car, you are better off being in the truck than in the car. Why is this? Many people imagine that the collision force exerted on the car is much greater than that experienced by the truck. To substantiate this view, they point out that the car is crushed, whereas the truck in only dented. This idea of unequal forces, of course, is false. Newton's third law tells us that both objects experience forces of the same magnitude. The truck suffers less damage because it is made of stronger metal. But what about the two drivers? Do they experience the same forces? To answer this question, suppose that each vehicle is initially moving at 8.0 m/s and that they undergo a perfectly inelastic head-on collision. (In an inelastic collision, the two objects move together as one object after the collision.) Each driver has a mass of 100.0 kg. Including the drivers, the total vehicle masses are 900kg for the car and 4100 kg for the truck. The collision time is 0.100 s. Choose coordinates such that the truck is initially moving in the positive x direction, and the car is initially moving in the negative x direction.

(i) What impulse did the truck driver experience from his seatbelt? (Sign matters!)

(j) What impulse did the car driver experience from his seatbelt? (Sign matters!)

(k) What is the average force on the truck driver from the seatbelt? (Sign matters!)

(l) What is the average force on the car driver from the seatbelt? (Sign matters!)

Answer 1