Question 19M.2.SL.TZ2.3
| Date | May 2019 | Marks available | [Maximum mark: 7] | Reference code | 19M.2.SL.TZ2.3 |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Calculate, Determine, Label, State | Question number | 3 | Adapted from | N/A |
The diagram shows the direction of a sound wave travelling in a metal sheet.
Particle P in the metal sheet performs simple harmonic oscillations. When the displacement of P is 3.2 μm the magnitude of its acceleration is 7.9 m s-2. Calculate the magnitude of the acceleration of P when its displacement is 2.3 μm.
[2]
Expression or statement showing acceleration is proportional to displacement ✔
so «» ✔
This was well answered at both levels.
The wave is incident at point Q on the metal–air boundary. The wave makes an angle of 54° with the normal at Q. The speed of sound in the metal is 6010 m s–1 and the speed of sound in air is 340 m s–1. Calculate the angle between the normal at Q and the direction of the wave in air.
[2]
✔
θ = 2.6° ✔
Many scored full marks on this question. Common errors were using the calculator in radian mode or getting the equation upside down.
The frequency of the sound wave in the metal is 250 Hz.
State the frequency of the wave in air.
[1]
f = 250 «Hz» OR Same OR Unchanged ✔
Many used a ratio of the speeds to produce a new frequency of 14Hz (340 x 250/6010). It would have helped candidates if they had been aware that the command term ‘state’ means ‘give a specific name, value or other brief answer without explanation or calculation.’
Determine the wavelength of the wave in air.
[1]
» ✔
The sound wave in air in (c) enters a pipe that is open at both ends. The diagram shows the displacement, at a particular time T, of the standing wave that is set up in the pipe.
On the diagram, at time T, label with the letter C a point in the pipe that is at the centre of a compression.
[1]
any point labelled C on the vertical line shown below ✔
eg:
This was answered well at both levels.