Q1 · 2021 · Paper 2Simple familiar3 marks
QUESTION 1 (3 marks)
A charge of 2.8 × 10–7 C experiences an electrostatic force of 5.2 × 10–1 N when placed near a charge of 3.2 × 10–7 C. Calculate the distance between the two charges.
WORKED SOLUTION
3 marksQCAA guide · typeset solution
ANSWER
See worked solution below.
Worked solution
𝐹=
1
4𝜋𝜀0
𝑄𝑞
𝑟2
𝑟2 =
1
4𝜋𝜀0
𝑄𝑞
𝐹
𝑟= √1
4𝜋𝜀0
𝑄𝑞
𝐹
= √9 × 109 × 2.8 × 10−7 × 3.2 × 10−7
0.52
Distance = 0.039 m (to 2 significant figures)
• recognises the scenario relates to Coulomb’s law
[1 mark]
• provides appropriate mathematical reasoning
[1 mark]
• calculates the distance [1 mark]
One QCAA sample method typeset for web; criterion wording is adapted from the official marking guide.
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