A Levels Physics (9702)•9702/12/M/J/18

Explanation
Force equilibrium in horizontal and vertical directions
Steps:
- Resolve forces vertically: tension's vertical component balances weight, so T cos θ = W.
- Resolve forces horizontally: tension's horizontal component balances P, so T sin θ = P.
- Divide horizontal by vertical equation: (T sin θ)/(T cos θ) = P/W, so P = W tan θ.
- Substitute T from vertical: T = W / cos θ, confirming both relations in C.
Why C is correct:
- Newton's first law requires net force zero; vertical equilibrium gives T cos θ = W directly from component resolution.
Why the others are wrong:
- A: Swaps components; P equals T sin θ, not W cos θ, and T exceeds W.
- B: Ignores angles; T ≠ P + W as forces are not collinear.
- D: Incomplete and lacks P = W tan θ relation.
Final answer: C
Topic: Equilibrium of forces
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