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In this lesson, we will learn how to calculate the change in the momentum of an object that experiences a given force for a given time.
Q1:
A mobile phone with a mass of 0.172 kg is dropped from a height of 1.5 m. The phone decelerates from the speed it gained by falling to rest in a time interval of 0.026 s.
What is the magnitude of the average force exerted on the phone by the ground?
What is the magnitude of the average force exerted on the phone by the ground if, rather than coming to rest, the phone rebounds from the ground, initially moving at a speed negligibly less than the speed at which it hit the ground?
Q2:
A rugby player of mass 105 kg is moving at 6.45 m/s and collides with a padded goalpost. The collision exerts a force on the rugby player in the opposite direction to his motion of 15.0 kN for 72.8 ms. At what speed does the rugby player move away from the goalpost?
Q3:
In a physics laboratory, two carts move on a track that produces negligible friction. The carts’ ends contain magnets so that the carts stick together if their ends contact each other. One cart has a mass of 0.675 kg and moves to the right at 0.750 m/s, while the other has a mass of 0.500 kg and moves to the right at 1.33 m/s, catching up with the first cart and colliding with it.
What is the speed of the carts after they collide?
The collision is repeated, this time with the 0.500 kg mass cart moving to the left. What is the velocity of the carts after they collide? Assume that motion to the right corresponds to positive velocity.
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