Circular Motion/Waves Practice Test Solutions
You are in the Rotor ride at Great Adventure. You have a mass of 60 kg, and are against
the wall in a round room with a radius of 3.0 meters, which is rotating at 4.0 m/s. From
above, the room is rotating clockwise.
1. Draw the view from above for this ride. Clearly indicate where you are, and the
direction of your velocity and acceleration.
Velocity: tangent to the circle
Acceleration: toward center of circle
2. What is the magnitude of the centripetal acceleration?
[a = 5.3 m/s]
3. What is the magnitude of the centripetal force?
[F = 320 N]
4. Explain, briefly, why you feel pressed back into the wall when you ride this ride,
and what is actually happening.
Because of inertia, your body tends to go in a straight line unless acted on by an external
force. While in this ride, that straight line will take you out of the circle. This makes you
*feel* like you are being pushed out of the circle.
5. The moon has a mass of 7.35 x 1022 kg. The earth has a mass of 5.98 x 1024 kg.
They are 4 x 108 meters apart. Determine the force between them.
[1.83 x 1020 N]
6. An astronaut has a mass of 100 kg. What is his weight on earth?
[1000 N]
7. An astronaut has a mass of 100 kg. His weight on the moon is 160 N. What is
the acceleration due to gravity on the moon?
[1.6 m/s²]
A 100 kg satellite is orbiting a small planet at a radius of 1,000,000 m. The satellite is
moving at 100 m/s.
8. What is the centripetal force on the satellite?
[1 N]
9. What is the mass of this small planet (given that is produces this force on the
satellite)?
[1.5 x 1020 kg]
10. Give 2 examples of transverse waves.
[Ocean Waves, Crowds in a Stadium doing “the wave”, wiggles on a string]
11. Give 1 example of a longitudinal wave.
[Sound]
12. Draw a periodic wave, and indicate the amplitude and wavelength.
[I can’t draw this here, look it up]
13. The speed of sound is 346 m/s. If it takes thunder 5 seconds to reach you, how far
away is the lightning?
[1730 m]
14. The speed of sound is 346 m/s. If a note has a frequency of 512 Hz, what is its
wavelength?
[0.676 m]
15. When a transverse wave moves through a medium, what is the action of the
particles of the medium?
[The particles move at right angles to the wave speed]
16. When an opera singer hits a high pitch note, a glass on the opposite side of the
opera hall shatters. Explain this phenomenon.
[The glass has one or more “natural frequencies” at which it will resonate. By
singing at this frequency, the singer causes the glass to vibrate violently, which
causes it to shatter]
17. You are standing by the side of the road, and an ambulance rushes past you.
What happens to the frequency of the siren’s sound as it passes you?
[As a result of the Doppler Effect, the frequency goes from high to low as the
ambulance passes you]