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Inquiry: Center of Gravity

Purpose: To observe how the weight of the beam on which the forces act behaves like a force concentrated at the center of gravity of the beam and to determine the conditions for equilibrium of several parallel forces.

Procedure for Part 1:

  • Mass a meter stick on a balance.

  • Locate the COG of the stick by balancing it on a narrow support.

  • Support the meter stick at some location OTHER than the COG and add a single clip and mass to bring the stick into balance.

  • In your notebook, draw the FBD and calculate the mass required at the COG to produce rotational equilibrium and compare this mass with the measured mass of the stick. Calculate the % error.

Procedure for Part 2:

  • Support the meter stick at the 0.20 m mark and hang a 1.0 kg mass at the 0.01m mark.

  • At the 0.1m mark hang a 0.5 kg mass, at the 0.4 m mark hang a 0.1 kg mass and at the 0.7 m mark hang a 0.2 kg mass.

  • In your notebook, draw the FBD and compute where a 0.1 kg mass and clip must be hung to produce rotational equilibrium. Compute a % error.

Inquiry Questions:

  1. A 20 m long rod with an uneven distribution of mass is being supported on both ends. The upward force on one end is 800 N while the other one is 600 N. Where is the COG? (show work)