Question

b)A uniform metre rule balances horizontally on a knife edge placed at the 54cm mark when a weight of 20 gf is suspended from one end.
(i)Draw a diagram of the arrangement.
(ii)What is the weight of the rule ?

Answer 1

Answer:

Weight mg (W) of rule produces an anti-clockwise moment about the knife edge O. In order to balance it, 20gf must be suspended at the end B to produce clockwise moment about the knife edge O. (ii) From the principle of moments, Anticlockwise moment = Clockwise moment W × (58-50) = 20gf × (100 − 58) W × 8 = 20gf × 42 W = 20gf x 42/8 = 105 gf