A meter stick balances at the 35.0cm mark whena 100g mass is hanging from the 20.0cm mark What is the mass of the meter stick?

Answer 1

Let "m" = mass of the stick.

g = gravitational acceleration

On the short side:

Stick alone . . . 0.35mg effectively hanging at 0.175 meter from the pivot

Hanging package . . . (0.1 kilogram x g) hanging at 0.15 meter from the pivot

Total moments: (0.35mg x 0.175) + (0.1g x 0.15) = 0.06125mg + 0.015g

On the long side:

Stick alone . . . 0.65mg effectively hanging at 0.325 from the pivot

Total moment = 0.21125mg

The moments on each side are equal.

0.21125mg = 0.06125mg + 0.015g

0.15mg = 0.015g

m = 0.1 kilogram = 100 grams