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Date November 2021 Marks available 3 Reference code 21N.2.HL.TZ0.2
Level Higher level Paper Paper 2 Time zone 0 - no time zone
Command term Determine Question number 2 Adapted from N/A

Question

A longitudinal wave travels in a medium with speed 340 m s−1. The graph shows the variation with time t of the displacement x of a particle P in the medium. Positive displacements on the graph correspond to displacements to the right for particle P.

Another wave travels in the medium. The graph shows the variation with time t of the displacement of each wave at the position of P.

A standing sound wave is established in a tube that is closed at one end and open at the other end. The period of the wave is T. The diagram represents the standing wave at t=0 and at t=T8. The wavelength of the wave is 1.20 m. Positive displacements mean displacements to the right.

Calculate the wavelength of the wave.

[2]
a.

Determine, for particle P, the magnitude and direction of the acceleration at t = 2.0 m s.

[3]
b.

State the phase difference between the two waves.

[1]
c.i.

Identify a time at which the displacement of P is zero.

[1]
c.ii.

Estimate the amplitude of the resultant wave.

[1]
c.iii.

Calculate the length of the tube.

[1]
d.i.

A particle in the tube has its equilibrium position at the open end of the tube.
State and explain the direction of the velocity of this particle at time t=T8.

[2]
d.ii.

Draw on the diagram the standing wave at time t=T4.

[1]
d.iii.

Markscheme

T=4×10-3 «s» or f=250«Hz» ✓

λ=340×4.0×10-3=1.361.4«m» ✓

 

Allow ECF from MP1.
Award [2] for a bald correct answer.

a.

ϖ=«2πT=»2π4×10-3  OR  1.57×103 «s−1» ✓

a=«ϖ2x0=1.57×1032×6×10-6=14.8»15 «ms−2» ✓

«opposite to displacement so» to the right ✓

b.

«±» π2/90°  OR  3π2/270° ✓

c.i.

1.5 «ms» ✓

c.ii.

8.0 OR 8.5 «μm» ✓


From the graph on the paper, value is 8.0. From the calculated correct trig functions, value is 8.49.

c.iii.

L = «34λ=» 0.90 «m» ✓

d.i.

to the right ✓

displacement is getting less negative

OR

change of displacement is positive ✓

d.ii.

horizontal line drawn at the equilibrium position ✓

d.iii.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.i.
[N/A]
c.ii.
[N/A]
c.iii.
[N/A]
d.i.
[N/A]
d.ii.
[N/A]
d.iii.

Syllabus sections

Core » Topic 2: Mechanics » 2.1 – Motion
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