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A solid cylinder fits snugly inside a larger pail, and the two are balanced by an equal mass on the other side of a scale. The cylinder is then suspended below the pail and lowered into water, making the scale tip toward the other mass. Balance is restored by pouring the water displaced by the cylinder into the pail.

Note: Lock the balance before you move it. To adjust the frame use the plumb bob. This apparatus is extremely top heavy so keep a hand on it while you transport it on a cart.

This demonstration shows that the buoyant force experienced by the solid cylinder when it is immersed in water is equal to the weight of the water the cylinder displaces. This is achieved by first immersing the cylinder in a beaker of water which is supported by the blocks. This causes the balance to tip due to the apparent lightening of the cylinder. Then the water from a different beaker is poured into the empty cylinder (which has the same empty volume as the solid cylinder) until the system comes into balance again.

Setup Instructions

1. Unlock the balance needle by turning the knob on the bottom near the center of the balance. If the needle is not centered, zero the balance by rotating the knob on the top center of the balance. Additionally, level the apparatus by screwing the legs up or down (so that plumb bob centered in its circle).

2. Fill one large beaker with water, and then use that water to carefully fill the second large beaker such that when the solid mass is immersed in the beaker it will remain completely immersed even when the balance is tilted.

3. Fill the smaller beaker with enough water to fill the empty cylinder.

Parts List

Archimedes Balance Apparatus in Room 326A

2 Large Beakers in B. Fluids & Mech, 1B

Small Beaker in B. Fluids & Mech, 1B

2 Blocks in A. Mechanics, 1A

Relevant Simulation

Demo Example:

Other Information

Archimedes' Principle

Real-Life Examples

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More Advanced Reading

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