PH 201 Supplemental Instruction 2014
Exam 3 Review
1. You are standing near the speaker at your local bar and register 100 dB. If the power
output of the speaker is 40 W, how far away are you standing from the speaker? Assume
the speaker emits sound isotropically.
2. You are driving at 20 m/s, and you honk your horn at the car in front of you. The horn
has frequency of 350 Hz. What speed is the car in front of you going if he hears the sound
with frequency of 400 Hz?
3. You and a friend are each holding an end of a string. Together you make a standing
wave. If the wavelength is 3m, what is the closest distance you and your friend can be to
each other? What is the velocity of this wave if the frequency is 200Hz? What is the
tension in the string if it has a linear mass density of 2 kg/m?
4. What are the first 3 frequencies for a pipe of length 2 m that is open at one end and closed
on the other? Draw what these first three waves look like.
5. A 6kg mass is attached to a massless spring. The mass is pushed (so the spring
compresses) 5 cm and then released. It reaches a maximum speed of 0.71 m/s, what is the
spring constant of the spring?
6. If the position of a 6kg mass is given by x(t) = 4cos(25t), what is the frequency of
oscillation? What is the spring constant of the spring?
7. The frequency of a transverse wave is 25 Hz. The wavelength of this wave is 100cm and
the amplitude is 0.5m. Write the equation of the wave with respect to time and position if
it is travelling in the negative x direction. What is the speed of the wave?
8. A simple pendulum swings through an angle of 5°. It has a length of 1.5 m. What is the
period of oscillation?
9. If the period of a physical pendulum is 3s, what is the length of the rod? The mass of the
rod is 2.3kg. (moment of inertia = (1/3)ML2)