What is the formula that relates force to momentum?

force = change in momentum / time


(there are two ways you can write this using symbols)


F = tΔp

 

F = tmvmu

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Using the ideas of momentum and force, explain why car crashes can cause injury to the passengers.

When there is a car crash, the car and the passengers decelerate rapidly.


They experience large forces because of the very fast change in momentum - and these large forces can cause injuries.

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Give 3 safety features of modern cars that reduce the risk of harm to passengers.

  1. Seat belts.
  2. Air bags.
  3. Crumple zones.

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How do seat belts work?

Seat belts stop you flying out of your seat during a car crash.


By stretching a little bit, they increase the time taken for the body's momentum to reach zero, and so reduce the forces on acting on the body.

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How do air bags work?

Air bags provide a soft surface to collide with during a car crash.


By being flexible, they increase the time taken for the body's momentum to reach zero, and so reduce the forces acting on the body

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How to crumple zones work?

Crumple zones are areas of a vehicle that are designed to crumple in a controlled way during in a collision.


By crumpling over time they increase the time taken for the passengers momentum to reach zero, and so reduce the forces acting on the bodies of the people in the car. 

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