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Turning Moment About a Pivot
Use the Physics Equations Sheet to answer this question. The child applies a force of 2.0 N on gear A. The perpendicular distance between the force and the pivot is 7.5 cm.
Calculate the moment of the force about the pivot.
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Marking points
- 1 Converts the perpendicular distance to 0.075 m.
- 2 Uses moment = force × perpendicular distance with the student's distance value.
- 3 Calculates 0.15 N m, with official consequential marking for an incorrectly converted distance.
Full-mark answer
7.5 cm = 0.075 m. M = Fd = 2.0 × 0.075 = 0.15 N m.
Why this answer loses marks
Uses the centimetre distance directly and labels the result in newton metres.
The distance must first be converted to metres; later correct equation work can then produce the required unit.