Middle School

17. A skateboard has a mass of 3.2 kg. If it slips out from a skateboarder and has a velocity of 1.0 m/s, what is the momentum of the skateboard?

18. You drop your physics textbook on your big toe. If the textbook has a mass of 2.18 kg and is in freefall, calculate the force when the book hits your foot.

19. Suppose that you lift your foot and kind of catch the book. I say "kind of catch" the book because as the book hits your foot, you slowly lower it to the ground. Will your big toe hurt more or less than it did in problem 18?

20. What was the change in momentum from problem 19 if it took half a second for the book to come to rest?

Answer :

Book will hit the foot with force 21.8 N

Explanation:

The momentum of any object = m v

here m is the mass of body and v is its velocity

Thus momentum P = 3.2 x 1 = 3.2 kg-m

As the book is falling freely , so it will fall with and acceleration g

The force exerted by it is = m g

Thus force = 2.18 x 10 = 21.8 N

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