THE TURNING EFFECT OF FORCES
2 marks · Normal| Diagram | Force (N) | Distance from pivot (m) | Angle to lever arm (°) |
|---|---|---|---|
| A | 40 | 0.2 | 90 |
| B | 60 | 0.1 | 0 |
| C | 80 | 0.05 | 90 |
| D | 100 | 0.01 | 90 |
Look at the table showing different forces applied to a door at various distances and angles from the hinge (pivot).
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
A shows the greatest turning effect (moment); B shows zero turning effect.
Also accept: A is greatest; B is zero; Maximum moment: A; zero moment: B
Common mistakes: Only looking at largest force, not considering distance or angle.
Show mark scheme and worked solution
Marking points
B1 · 1 mark · Correctly identifies Diagram A as showing the greatest moment.
B2 · 1 mark · Correctly identifies Diagram B as showing zero moment (angle 0°).
Worked solution
Moment = Force × Distance × sin(angle). For A, 40 × 0.2 × sin(90°) = 8 Nm. For B, angle is 0°, sin(0°) = 0 so there is no moment. A is the maximum, B is zero.