A uniform metre rule is balanced at 30cm mark when mass 50cm is hanging from its zero cm mark.calculate the weight of the rule .
Let X be the weight of the meter rule. The meter rule is balanced at the 30 cm mark, which means the moments on either side of the fulcrum (30 cm mark) are equal. The clockwise moment = the counterclockwise moment.
The clockwise moment is caused by the weight of the hanging mass (50 g = 0.5 N) acting at 30 cm (the distance from the fulcrum to the 0 cm mark). So, the clockwise moment = 0.5 N * 30 cm.
The counterclockwise moment is caused by the weight of the meter rule (X) acting at its center of mass, which is the 50 cm mark (half of the length of the meter rule). The distance from the fulcrum to the center of mass = 50 cm - 30 cm = 20 cm. So, the counterclockwise moment = X * 20 cm.
Now, we set the clockwise moment equal to the counterclockwise moment and solve for X:
0.5 N * 30 cm = X * 20 cm
15 N cm = 20X cm
X = 15 N / 20
X = 0.75 N
So, the weight of the meter rule is 0.75 N.