Question

The diagram below (Fig. 1.32) shows a uniform bar
supported at the middle point 0. A weight of 40 gf is
placed at a distance 40 cm to the left of point 0
How can you balance the bar with a weight of
80 gf ?
​

Answer 1

Given info : The diagram shows a uniform bar supported at the middle point, O. A weight of 40gf is placed at a distance 40cm to the left of point O.

To find : how can you balance the bar with a weight of 80gf ?

solution : To balance the bar, net torque at point O must be zero.

let a weight of 80gf is placed at x distance to the right of point O.

⇒40gf × 40cm (←) + 80gf × x (→) = 0

⇒40gf × 40cm (←) - 80gf × x (←) = 0

⇒40gf × 40cm = 80gf × x

⇒x = 20 cm

Therefore a weight of 80gf must be placed at 20cm to the right of point O.