Question

When a mass of 50g is hung from 5cm mark of a uniform meter rule. The rule balance on a knife edge placed at the 35cm mark . what is the weight of d meter rule? (take g:10ms-2).

Answer 1

the 50 g mass is 30 cm from the balance point

the center of mass of the meter rule is 15 cm from the balance point
... half the distance ... twice the mass

the mass of the rule is twice 50 g
... weight is ... m * g ... .05 kg * 10 m/s^2 = .5 N

Answer 2

oops ... forgot to double the 50 g

weight of the rule is ... 1 N

Answer 3

moments in grams * centimeters about 0 cm mark
clockwise: 50 * 5 + m * 50
counterclockwise: (m+50) * 35
so
250 + 50 m = 35 m + 1750
15 m = 1500
m = 100 grams which is 0.100 kilograms
weight = mass * g = 0.100 kg * 10 meters /second^2 = 1 Newton