1. Galileo found that a ball rolling down one incline will pick up enough speed to roll up another. How high will it roll compared with its initial height if (a) there is no friction and (b) if there is?
2. Many automobile passengers suffer neck injuries when struck by cars from behind. How does Newton’s law of inertia apply here? How do headrests help to guard against this type of injury?

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@ybarrap

I know that for (1) without friction the ball will always reach the same height every time.

You are correct. Have you studied potential and kinetic energy?

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