(a) Anticlockwise moment = F × r

= 40 gf × (50 – 10) cm

= 40 × 40

= 1600 gf cm

Clockwise moment = F × r

= 20 gf × (90 – 50) cm

= 20 × 40

= 800 gf cm

So, the meter rule will not be in equilibrium. It will turn in anticlockwise direction.

(ii) To balance the rule in equilibrium 40gf should be kept on right side.

Let distance from middle = d cm

So clockwise moment becomes

Extra moment = 1600 gf cm – 800 gf cm

= 800 gf cm

Now, 40 × d = 800

⇒ d = 800\over 40 = 20 cm

So, the additional weight should be placed at 70cm mark to bring the rule in equilibrium.