Q25 · 2021 · Paper 1Simple familiar4 marks
QUESTION 25 (4 marks)
The graph shows the centripetal forces required to keep objects with different mass in uniform circular motion with a constant speed and constant radius of 20 cm.
Determine the speed of the objects.
WORKED SOLUTION
4 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
𝐹= 𝑚𝑣2
𝑟
gradient =
𝑣2
𝑟
gradient =
6.0 − 0.0
0.2 − 0.0 = 30
𝑣= √0.2 × gradient
𝑣= √0.2 × 30
𝑣= 2.4 m s−1
Speed = 2.4 m s–1 (to 1 decimal place)
• recognises how the scenario relates to 𝐹=
𝑚𝑣2
𝑟
[1 mark]
• identifies line of best fit [1 mark]
• provides appropriate mathematical reasoning
[1 mark]
• determines the speed [1 mark]
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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