Table of Mechanics Demonstration List of Mechanics Equipment & Supplies Lecture Demonstrations

Persistence of Motion (Air Track), 1F30.10

Topic and Concept:

Location:

• Floor Item: ME, South Wall on shelf brackets

Abstract:

A cart on a low-friction air track is given a velocity which remains roughly constant as per Newton's first law.

 Equipment Location ID Number 2.25m Air Track ME, South Wall on shelf brackets A Glider ME, Bay A4, Shelf #2 Air Hose ME, South Wall on shelf brackets Air Supply Located rooms 2103, 2241, and 2223 4A.EQ100

Important Setup Notes:

• This demonstration requires a supply of compressed air at HVHP.

• A Red & White Gas Cart will need to be installed under the lecture tables and the air hose will need to be connected to the supply line within the stage floor.

Setup and Procedure:

1. Place air track on lecture bench.
2. Level the track using the set screws on each leg.
3. Connect the track to the air supply using the air hose.
4. Place air glider on track.
5. Let the air flow into the track by opening the supply valve.
6. Give the air glider a push to give it an initial velocity.

Cautions, Warnings, or Safety Concerns:

• N/A

Discussion:

The kinematic version of Newton's first law says that a body in motion tends to stay in motion moving in a straight line unless acted upon by a force. This is exactly what is happening here. The glider is given an initial velocity being accelerated by the lecturer's hand. Upon release, the glider maintains its final velocity. The air track provides a low-friction surface for the glider to move on so not much energy can be lost as heat. Thus the speed will remain roughly constant. The direction will change, however. The velocity will switch between v0 and -v0 each time it hits a bumper in an elastic collision whereby the direction of its momentum is reversed.

Videos:

References:

• N/A

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