Kevin S. Huang

2007: Problem 20

Topic: Collisions
Concepts: Kinetic energy

Solution:

The kinetic energy is given by

E=\frac{1}{2}mv^2 \propto v^2

Since each collision reduces $E$ by a factor of $2$ , $v$ is reduced by a factor of $\sqrt{2}$ . We have

\sqrt{2}^6=8

so 6 collisions would reduce $v$ by a factor of $8$ . Thus, the answer is C.

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2007, F=ma Exam

Fma: Collisions, Kinetic energy

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