Question 9
Equilibrium of ForcesA uniform metre rule QR is balanced on a knife edge which is 55 cm from R. When a mass of 10 g is hung at P as shown in Fig. 2, the mass of the metre rule is
- A.550 g
- B.350 g
- C.70 g
- D.35 g
Show the answer and explanation
Answer: C (70 g)
Explanation
From R, P is at 90 cm, the pivot at 55 cm and the rule's centre of gravity at 50 cm. Moments: 10 × 35 = m × 5, so m = 70 g.