What are waves?
4 marks · NormalA student notices that a wave pulse on a rope travels 4 m in 2 s. She then produces another pulse, which covers 10 m in 5 s.
Calculate the speed of the wave in the first observation.
Calculate the speed of the wave in the second observation.
Suggest one possible reason for any difference in wave speed between the two observations.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 2.0 m/s · must show Working: 4/2 = 2.0
(b) 2.0 m/s · must show Working: 10/5 = 2.0
(c) Possible differences: the rope tension or the force used could be different, affecting the speed.
Common mistakes: Mistakes in division; Using the wrong time or distance; Not giving a realistic cause for difference
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Selects correct formula: speed = distance / time.
A1 (a) · 1 mark · Performs calculation: 4 / 2 = 2.0 m/s.
A2 (b) · 1 mark · Performs second calculation: 10 / 5 = 2.0 m/s.
B1 (c) · 1 mark · Suggests a possible cause, e.g. different rope tension, force, or medium.
Worked solution
a) Speed = distance / time = 4 m / 2 s = 2.0 m/s
b) Speed = 10 m / 5 s = 2.0 m/s
c) A possible reason for any difference could be change in rope tension or how strongly the pulse was sent.