# Warm-Up Exercise for lecture 25

## Due 8:00 am, Tues, Dec 2

Physics 105, Fall 2008

Some object is moving back and forth in harmonic motion. Where is the
acceleration of that object greatest?

☐ at the midpoint of the motion

☑ at the end points of the motion

☐ same value at every point

Consider a mass *m* hanging on a spring. We pull the weight downward and
then release it so that it oscillates up and down. If we repeat this
on the moon with the same weight and the same spring, the frequency of the
oscillation will be:

☐ larger

☐ smaller

☑ the same

Two students play with an
extra-long Slinky. The student
on the left end sends waves to the other student by shaking her end back and
forth. After the waves die down, both students take a step backwards and try it
again. How will the speed of the waves now compare to the previous waves?

☑ They will be faster

☐ They will be slower

☐ They will go the same speed

Ralph is confused about pendulums. He read in the textbook that the
period *T* of a pendulum depends on its length *L* and on the
acceleration of gravity *g*,but does not depend on its mass. Ralph thinks
that heavier pendulums should swing with a longer period. After all, if he puts
a heavier weight on the end of the spring, it oscillates more slowly.
Can you help Ralph understand this?

The "restoring force" is provided by gravity (by a component, at least), and so is proportional to mass. Since the acceleration is equal to F/m, the masses cancel out. This is the same reason that all objects fall at the same rate.

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