O Levels Physics (5054)•5054/12/M/J/21
Explanation
Equilibrium requires balanced forces with zero net force
Steps:
- Identify forces on each block: all arrows are 10N magnitude.
- For block P: two horizontal forces oppose each other, canceling to zero net force.
- For block Q: vertical upward force unbalanced by downward, resulting in net downward force.
- For block R: two vertical forces oppose, canceling to zero net force.
- For block S: horizontal and vertical forces unbalanced, resulting in net force.
Why A is correct:
- Newton's first law states an object is in equilibrium if net force is zero; P and R satisfy this as forces balance in all directions.
Why the others are wrong:
- B: Q and S have unbalanced forces, violating zero net force condition.
- C: Q has net downward force, so not in equilibrium.
- D: Q and S have nonzero net forces, preventing equilibrium.
Final answer: A
Topic: Balanced and unbalanced forces
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