Newton's Laws

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MCAT Physical › Newton's Laws

Questions 1 - 2

A 1kg plate falls from a shelf 1m above the ground and breaks into three pieces of mass 0.1kg, 0.4kg and 0.5kg. What is the total energy of the scattered pieces?

$9.8 \textup{ J}$

$20 \textup{ J}$

We must know the velocity of each piece to solve

We must know the shape of the plate to solve

$5 \textup{ J}$

Explanation

This is a conservation of energy question. The event is the collision. The initial energy can be calculated by gravitational potential energy:

$U=(1kg)(9.8\frac{m}{s^2})(1m)=9.8J$

The final total energy must be the same. The energy of the scattered pieces must add to

A ball is rolled into a stationary ball. If the heavier ball applies a force on the smaller ball, what force will the smaller ball apply on the large ball?

Explanation

The answer to this question lies within Newton's third law: for every action, there is an equal and opposite reaction. If the large ball applies a force on the smaller ball, the smaller ball will apply a force on the large ball in the opposite (negative) direction.

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