Periodic Waves AP Physics 2 MCQ – Exam Style Questions etc.
Periodic Waves AP Physics 2 MCQ
Unit 14: Waves , Sound , and Physical Optics
Weightage : 15–18%
Exam Style Practice Questions , Periodic Waves AP Physics 2 MCQ
Question: (7 points, suggested time 13 minutes)
A transverse wave travels to the right along a string.
(a) Two dots have been painted on the string. In the diagrams below, those dots are labeled P and Q.
i. The figure below shows the string at an instant in time. At the instant shown, dot P has maximum displacement and dot Q has zero displacement from equilibrium. At each of the dots P and Q, draw an arrow indicating the direction of the instantaneous velocity of that dot. If either dot has zero velocity, write “v = 0” next to the dot.
ii. The figure below shows the string at the same in stant as shown in part (a)i. At each of the dots P and Q, draw an arrow indicating the direction of the instantaneous acceleration of that dot. If either dot has zero acceleration, write “a = 0” next to the dot.
The figure below represents the string at time t = 0, the same instant as shown in part (a) when dot P is at its maximum displacement from equilibrium. For simplicity, dot Q is not shown.
(b)
i. On the grid below, draw the string at a later time t = T/4, where T is the period of the wave.
Note: Do any scratch (practice) work on the grid at the bottom of the page. Only the sketch made on the grid immediately below will be graded.
ii. On your drawing above, draw a dot to indicate the position of dot P on the string at time t = T/4 and clearly label the dot with the letter P.
(c) Now consider the wave at time t = T. Determine the distance traveled (not the displacement) by dot P between times t = 0 and t = T.
Answer/Explanation
Ans:
(a)
(i)
(ii)
(b) (i)
(c)
– 8 → 8 → -8
16 + 16 32 cm
Question
In the graphs that follow, a curve is drawn in the first graph of each pair. For the other graph in each pair, sketch the curve showing the relationship between the quantities labeled on the axes. Your graph should be consistent with the first graph in the pair.
Answer/Explanation
Ans:
c) simple graph with 1.5x the frequency
d) Graphs are based on the Doppler equation. The graph given in the problem is for a moving observer. Which is based on ƒ’ = ƒ\(\frac{(v_{snd}+v_{obs})}{v^{snd}}\). As the observer’s velocity increases, the frequency increases linearly with it as is shown in the problem
The new graph is based on a source moving towards you. ƒ’ = ƒ \(\frac{v_{snd}}{(v^{snd}-v_{source})}\). As can be seed from this equation, as the source increases velocity, the frequency increases but when the source approaches the speed of sound, the frequency approaches ∞ and becomes undefined so has a limit to it unlike in the first graph.
