Intro to Waves

Which of the following makes a correct claim about whether sound waves are transverse or longitudinal waves, and also provides a valid justification for the claim?

A) Sound waves are transverse waves. They transfer energy between locations.

B) Sound waves are transverse waves. Particles in the medium move perpendicular to the direction of wave propagation.

C) Sound waves are longitudinal waves. They do not transfer energy between locations.

D) Sound waves are longitudinal waves. Particles in the medium move parallel to the direction of wave propagation.

D) Sound waves are longitudinal waves. Particles in the medium move parallel to the direction of wave propagation.

Two students are experimenting with wave pulses on a string, as shown in the figure. The student on the left holds one end of the string. The other end of the string passes over a pulley, held by the student on the right, and is attached to a cylinder that hangs vertically. In two experimental trials, a wave pulse is created and travels to the right along the string. In the first experimental trial, the students use nearly the full length of the string. In the second trial, they use approximately half the length of the string. The amplitude of the wave pulse is the same in both trials.

Which of the following correctly compares the propagation speed of the pulse in the two trials, and provides evidence or reasoning that helps support the claimed comparison?

A) The pulse speed is faster in the first trial. The pulse travels along a greater length of string in the first trial.

B) The pulse speed is faster in the first trial. The pulse travels along a more massive section of string in the first trial.

C) The pulse speed is the same in both trials. The pulse’s amplitude is the same in the two trials.

D) The pulse speed is the same in both trials. The string’s tension and mass per length are the same in the two trials.

D) The pulse speed is the same in both trials. The string’s tension and mass per length are the same in the two trials.

Speed of a wave only depends on the tension and linear density (mass per length) of a string.

Waves travel along three different strings: String 1, String 2, and String 3. Each string is made of the same material but does not necessarily have the same diameter. The mass per length of each string and the tension in each string are given in the table. Which of the following correctly compares the speeds v1, v2, and v3 of the waves on strings 1, 2, and 3, respectively?

A) v1 = v2 = v3

B) (v1 = v3) > v2

C) v3 > (v1 = v2)

D) v3 > v1 > v2

D) v3 > v1 > v2

String 1: 1:1

String 2: 2:1

String 3: 1:2

The figure shows one end of a string connected to a pulse generator and the other end of the string passing over a pulley with a block hanging from it. The pulse generator can create wave pulses that travel along the horizontal length of the string. Which of the following changes to the configuration would cause an increase in the speed at which pulses propagate along the string?

A) Hang a block of less mass from the string.

B) Hang a block of greater mass from the string.

C) Move the pulse generator to the right so the horizontal length of the string is shorter.

D) Move the pulse generator to the left so the horizontal length of the string is longer.

B) Hang a block of greater mass from the string.

In order to increase speed, increase the tension and decrease linear density (mass/lenght).

Tension is a force.

F = ma

Therefore, by increasing the mass, tension will also increase.