Question

A metre scale is pivoted at its midpoint when the various masses are suspended on it as shown in Fig. From which point will you suspend a 50 g mass in order to keep the ruler in equilibrium?

Answer 1

Given: Pivot at 50 cm

80 gf acts at 20 cm:

Moment = 80 × (50 − 20)

= 80 × 30 

= 2400 gf cm

40 gf acts at 60 cm:

Moment = 40 × (60 − 50)

= 40 × 10

= 400 gf cm

Let the 50 g mass be suspended at a distance xx to the right of the pivot.

For equilibrium:

2400 = 400 + 50 x

50 x = 2000

x = 40 cm

So, the position on the metre scale is:

50 + 40 = 90 cm