Most of us know intuitively that in a head-on collision betweena large dump truck and a subcompact car, you are better off beingin the truck than in the car. Why is this? Many people imagine thatthe collision force exerted on the car is much greater than thatexerted on the truck. To substantiate this view, they point outthat the car is crushed, whereas the truck is only dented. Thisidea of unequal forces, of course, is false; Newton's third lawtells us that both objects are acted upon by forces of the samemagnitude. The truck suffers less damage because it is made ofstronger metal. But what about the two drivers? Do they experiencethe same forces? To answer this question, suppose that each vehicleis initially moving at 6.40 m/s and that they undergo a perfectlyinelastic head-on collision. Each driver has mass 72.0 kg.Including the masses of the drivers, the total masses of thevehicles are 800 kg for the car and 4,000 kg for the truck. If thecollision time is 0.100 s, what force does the seat belt exert oneach driver? force on truck driver N force on car driver N
