Q2 · 2025 · Paper 2Simple familiar5 marks
QUESTION 2 (5 marks)
A rock with a mass of 0.15 kg is tied to a piece of string and spun in a horizontal circle in the air.
a)[2 marks]
Explain how the rock can travel at a constant speed and accelerate at the same time.
b)[3 marks]
A force of 4.0 N is exerted on the string, and the rock moves at a constant speed of .
Calculate the length of the string in metres. Show your working.
WORKED SOLUTION
5 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
a) The rock can travel with a constant speed but, since it is moving in a circle, it is changing direction. Since there is a change in velocity, the rock is accelerating.
b)
Length of string =
recognises that circular motion means direction changes
explains relationship between change in velocity and acceleration
recognises that the scenario relates to centripetal force on an object
provides appropriate mathematical reasoning
calculates length of the string
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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