Sarah, who has a mass of 55 kg, is riding in a car at 20 m/s. She sees a cat cro

Question

Sarah, who has a mass of 55 kg, is riding in a car at 20 m/s. She sees a cat crossing the street and slams on the brakes! Her seatbelt stops her from flying forward, bringing her to rest in 0.5 seconds. How much force did the seatbelt put on Sarah?

A big league hitter attacks a fastball! The ball has a mass of 0.16 kg. It is pitched at 38 m/s. After the player hits the ball, it is now traveling 44 m/s in the opposite direction. The impact lasted 0.002 seconds. How big of a force did the ballplayer put on that ball?

Someone fires a 0.04 kg bullet at a block of wood that has a mass of 0.5 kg. (The block of wood is sitting on a frictionless surface, so it moves freely when the bullet hits it). The wood block is initially at rest. The bullet is traveling 300 m/s when it hits the wood block and sticks inside it. Now the bullet and the wood block move together as one object. How fast are they traveling?

Explanation / Answer

Change in momentum = force multiplied by time.

m(Vf - Vi ) =F * t

m(Vf - Vi ) = 55(0-20)= -1100

F = -1100/0.5= -2200

-2200 Kg/m^2 force is exerted in opposite direction by seat bealt

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