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Figure 6 shows four forces, P, Q, R and S, acting on a rod - Edexcel - GCSE Physics - Question 4 - 2019 - Paper 1
Question 4
Figure 6 shows four forces, P, Q, R and S, acting on a rod. The rod can rotate around an axle. Which force will make the rod rotate about the axle?
Worked Solution & Example Answer:Figure 6 shows four forces, P, Q, R and S, acting on a rod - Edexcel - GCSE Physics - Question 4 - 2019 - Paper 1
Step 1
Which force will make the rod rotate about the axle?
Answer
The correct answer is force Q. This is because force Q is applied perpendicular to the rod, creating a moment about the axle. In contrast:
- Force P does not produce a moment because its line of action passes through the axle, resulting in zero distance to pivot and thus zero torque.
- Force R also does not produce any moment about the axle; its line of action is parallel to the line connecting the point of rotation, yielding zero lever arm.
- Force S similarly does not generate a moment, as its application point is aligned with the axle itself.
In conclusion, among all forces, only force Q creates a rotational effect around the axle.