Model Arm

In this model of the human bicep-arm system, a rod pivots about one of its ends as shown in the photo. Approximately 10 cm from that end, tension in a chain exerts a measurable force on the rod. Also, masses on a mass hanger loads down the rod's farther end. Students determine the value of tension read on the spring scale.

Setup:

Set up the equipment as shown in the image above.

Add masses and take measurements. Have students calculate the tension in the spring.

Notes:

None

Courses Used In:

• PHY 10111

• PHY 10310

• PHY 10410

• PHY 30210

Discussion and Polling Questions:

• What is the net force in each situation? The net torque?

• Why can't we use the net force to calculate the tension in the string?

• Do we need to know the mass of the rod?

Equipment Needed:

• Ring Stand

• Bar for Model Arm

• Spring Scale with Chain

• Masses and Mass Hangers

• Meter Stick

• Protractor