DP Physics (last assessment 2024)

Question 21M.2.SL.TZ1.6b.i

Date	May 2021	Marks available	[Maximum mark: 2]	Reference code	21M.2.SL.TZ1.6b.i
Level	SL	Paper	2	Time zone	TZ1
Command term	Show that	Question number	b.i	Adapted from	N/A

b.i.

[Maximum mark: 2]

21M.2.SL.TZ1.6b.i

On a guitar, the strings played vibrate between two fixed points. The frequency of vibration is modified by changing the string length using a finger. The different strings have different wave speeds. When a string is plucked, a standing wave forms between the bridge and the finger.

The string is displaced 0.4 cm at point P to sound the guitar. Point P on the string vibrates with simple harmonic motion (shm) in its first harmonic with a frequency of 195 Hz. The sounding length of the string is 62 cm.

(b.i)

Show that the speed of the wave on the string is about 240 m s⁻¹.

[2]

Markscheme

$λ = 2 l = 2 \times 0.62 = « 1.24 m »$ ✓

$v = f λ = 195 \times 1.24 = 242 « {m s}^{- 1} »$ ✓

Answer must be to 3 or more sf or working shown for MP2.

Syllabus sections

Core

Core » Topic 4: Waves » 4.2 – Travelling waves

Core » Topic 4: Waves

Question 21M.2.SL.TZ1.6b.i

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