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AQA · GCSE · Combined Science · Higher

Maximum force the magnet can exert calculation

Q01.4 3 marks

The student added more paperclips to one end of the magnet. The maximum number of paperclips the magnet could hold was 20. Each paper clip had a mass of 1.0 g. Gravitational field strength = 9.8 N/kg.

Calculate the maximum force the magnet can exert.

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Marking points

  1. 1 Convert the mass of one paper clip from grams to kilograms: 1.0 g=0.0010 kg1.0\ \mathrm{g}=0.0010\ \mathrm{kg}.
  2. 2 Use W=mgW=mg to calculate the weight of one paper clip: 0.0010×9.8=0.0098 N0.0010 \times 9.8 = 0.0098\ \mathrm{N}.
  3. 3 Multiply the weight of one paper clip by 20 to get the maximum force: 0.0098×20=0.196 N0.0098 \times 20 = 0.196\ \mathrm{N}.

Full-mark answer

1.0 g=0.0010 kg1.0\ \mathrm{g}=0.0010\ \mathrm{kg} Weight of one paper clip =0.0010×9.8=0.0098 N=0.0010 \times 9.8=0.0098\ \mathrm{N} Maximum force =0.0098×20=0.196 N=0.0098 \times 20=0.196\ \mathrm{N}.

Why this answer loses marks

0.0010×9.8=0.0098 N0.0010 \times 9.8 = 0.0098\ \mathrm{N}

This is the weight of one paper clip only. The magnet holds 20 paper clips, so the answer must be multiplied by 20.

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