Most of us know intuitively that in a head-on collisionbetween a large dump truck and a subcompact car, you arebetter off being in the truck than in the car. Why is this? Manypeople imagine that the collision force exerted on the car ismuch greater than that exerted on the truck. To substantiatethis view, they point out that the car is crushed, whereas thetruck is only dented. This idea of unequal forces, of course,is false; Newton’s third law tells us that both objects are actedupon by forces of the same magnitude. The truck suffersless damage because it is made of stronger metal. But whatabout the two drivers? Do they experience the same forces?To answer this question, suppose that each vehicle is initiallymoving at 8.00 m/s and that they undergo a perfectly inelastichead-on collision. Each driver has mass 80.0 kg. Includingthe masses of the drivers, the total masses of the vehicles are800 kg for the car and 4.00 x 103 kg for the truck. If the collisiontime is 0.120 s, what force does the seat belt exert oneach driver?
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 exerted on the truck. To substantiate
this view, they point out that the car is crushed, whereas the
truck is only dented. This idea of unequal forces, of course,
is false;
upon by 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 8.00 m/s and that they undergo a perfectly inelastic
head-on collision. Each driver has mass 80.0 kg. Including
the masses of the drivers, the total masses of the vehicles are
800 kg for the car and 4.00 x 103 kg for the truck. If the collision
time is 0.120 s, what force does the seat belt exert on
each driver?
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