Question 2
Equilibrium of ForcesIn Fig. 1, PT is a uniform metre rule pivoted at R, the 70 cm mark. Two forces 0.1 N and 0.4 N are applied at Q, the 60 cm mark and S, the 85 cm mark. If the metre rule is kept in equilibrium by the forces and its weight, then the weight of the metre rule is
- A.0.25 N
- B.0.30 N
- C.0.35 N
- D.0.50 N
- E.0.56 N
Show the answer and explanation
Answer: A (0.25 N)
Explanation
The weight acts at the 50 cm mark, 20 cm from the pivot. Moments about R: W × 20 + 0.1 × 10 = 0.4 × 15, so 20W = 5 and W = 0.25 N.