Physics Demo Number: 141

Approximate

Run Time: 5 min

Coupled Linear and Angular Acceleration Persisting For Several Minutes

Demo Description

A mass attached to a string wound securely around a pulley attached to a weighted bicycle wheel is allowed to fall vertically and impart angular acceleration to the wheel.

When the mass bottoms on the string, the motion of the wheel winds the string and mass back up.

The up/down motion of the mass and coupled wheel persists for several minutes.

Scientific Principles

The linear acceleration of a mass coupled to a wheel by a string wound securely around a pulley attached to the wheel's axle is the wheel's angular acceleration times the radius of the pulley.

Equipment

Yellow nylon cord
1 Kg hooked mass
Small Angular Momentum Bike Wheel

Equipment Location

[E-4-1]

Instructions

The first two photos show the old way of connecting the cord to the drive pulley. Now the cord is permanently attached through the hole where the pin was located.

Subsequent attachment of about 1 kg of mass to the other end of the string and winding up the string around the pulley gives one a dynamic system with enough energy that it will wind down and back up for about 3 to 5 minutes, with the linear acceleration of the mass coupling to the wheel and causing it to undergo angular acceleration.

The third photo shows the bike wheel mounted toward the top of one of the big tripod stands with the help of a table clamp.