Statics of Fluids: Archimedes' Principle

PIRA Class: 2B40.20

Purpose:
To demonstrate that the buoyant force is equal to the weight of the displaced water.

Description:
An object hung from a spring scale is lowered into water such that the spring scale reading and the weight of the displaced water can be measured.

1. Set the catcher cup atop the digital scale. Fill the overflow cup to where it just starts to overflow into the catcher cup. [The wooden block from Shelf 114 works well for setting the overflow cup at the correct height.]

2. Zero the digital scale.

3. Hang the cylinder from a spring scale and hang the spring scale from a ring stand. Note the spring scale reading before submerging any of the cylinder. [You may need to adjust the zero on the spring scale before hanging the cylinder.]

4. Gradually lower the cylinder into the overflow cup causing some water to flow into the catcher cup.

5. Note the new readings on the spring scale and the digital scale.

Example values: 

• spring scale reading when not submerged: 675 g

• spring scale reading when partially submerged: 500 g

• digital scale reading (displaced water): 188 g.

Equipment:
Cylinder and overflow and catcher cups (all in Archimedes' principle container), spring scale, digital scale, ring stand. (Vartaions: Use alcohol or oil in place of water.)

Web Simulation:

2B40.20: Archimedes' Principle - YouTube 

Location:
Shelf 162, Shelf 116 (spring scale and digital scale), Shelf 153 (ring stand)