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JAMB Physics 1981 Question 41

Question 41

Equilibrium of Forces

A particle is under the action of three forces in equilibrium. Two of the forces are as shown in Fig. 5. The third force is

Diagram for this question
  1. A.80 N along P
  2. B.160 N at 60° to P
  3. C.40√2 N at 45° to either P or Q
  4. D.0 N
  5. E.40√2 N at 30° to Q.
Show the answer and explanation

Answer: C (40√2 N at 45° to either P or Q)

Explanation

The two perpendicular 40 N forces have a resultant of √(40² + 40²) = 40√2 N at 45° between them. The third force must be equal and opposite to this, 40√2 N along the line at 45° to P and Q.