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JAMB Physics 1983 Question 3

Question 3

Equilibrium of Forces

Consider the three forces acting at O and in equilibrium as shown in Fig. 1. Which of the following equations is/are CORRECT? I. P1 cos θ1 = P2 cos θ2 II. P3 = P1 cos θ1 + P2 cos θ2 III. P1 sin θ1 = P2 sin θ2

Diagram for this question
  1. A.I only
  2. B.II only
  3. C.III only
  4. D.II and III only
  5. E.I and III only.
Show the answer and explanation

Answer: D (II and III only)

Explanation

Resolve horizontally: the components of P1 and P2 to the right together balance P3, so II is true. Resolve vertically: the upward part of P1 balances the downward part of P2, so III is true. I is not generally true.