Question

In this week's lab, suppose I have a good standing wave with three bumps. While keeping the frequency and the length of the string the same, if I pull down the hanging weight, what's likely to happen to the number of bumps?

Question 1 options:

	a. Nothing will happen.
	b. The wave will disappear immediately, and even if I keep pulling down on it, no more waves will appear.
	c. The wave will disappear immediately, but if I keep pulling down on it, a wave with three bumps will reappear.
	d. The wave will disappear immediately, but if I keep pulling down on it, a wave with four bumps will appear.
	e. The wave will disappear immediately, but if I keep pulling down on it, a wave with two bumps will appear.

One of the students reported to his TA that the fundamental mode for his lab setup yielded a wavelength that is four times the length of the wire that he used. What could the TA conclude from his student's statement?

Question 2 options:

	a. The student could be right.
	b. The student is probably wrong. Perhaps, this is because he forgot to tension the string appropriately.
	c. The student is definitely wrong as there can never be a fundamental mode on the string, with the experimental setup of this lab, with a wavelength that is four times the length.
	d. The student is definitely wrong as the wavelength should be equal to the length of the string for the fundamental mode of vibration for the experimental setup of this lab.

Another student reported to his TA that he increased the drive frequency by a factor of two to go from a 5-node resonance to 3-node resonance. Which of these TA conclusions is correct?

Question 3 options:

	a. The student is wrong as the frequency needs to be decreased.
	b. The student is not quite correct, but deserves 50% grade, as the answer is a factor of four rather than two.
	c. The student is not quite correct, but deserves 50% grade, as the answer is a factor of square root two rather than two.
	d. The student could be right.

Answer 1

Question 1 :

Suppose I have a good standing wave with three bumps. While keeping the frequency and the length of the string the same, if I pull down the hanging weight, what's likely to happen to the number of bumps?

b. The wave will disappear immediately, and even if I keep pulling down on it, no more waves will appear.

Question 2 :

One of the students reported to his TA that the fundamental mode for his lab setup yielded a wavelength that is four times the length of the wire that he used. What could the TA conclude from his student's statement?

a. The student could be right.

Question 3 :

Another student reported to his TA that he increased the drive frequency by a factor of two to go from a 5-node resonance to 3-node resonance. Which of these TA conclusions is correct?

b. The student is not quite correct, but deserves 50% grade, as the answer is a factor of four rather than two.