Experiment I

Goal: To illustrate the properties of constant acceleration as they relate to constrained motion with respect to gravity.

Equipment: 1x Air Track, 2x stop watch, 1x protractor, graphing paper, pencils

Method: Set the air track at regular intervals of 10 degrees, starting at 10 degrees and going to 90 degrees. Starting with the air track car at the top of the track -- with respect to ground -- measure the time it takes to reach the bottom of the track. Log this information in a table with the independent entry as degree of elevation and the dependent entry as time to reach bottom. When all angles have been recorded log these data on a graph.

Discussion: What happens as the angle becomes closer to 90 degrees? What does this say about the direction of force/acceleration? What would the graph look like if the force was always directed parallel to the air track? Perpendicular to the air track?

Going further (maybe too far): What is the direction of motion? It is always along the air track, regardless of angle. What is the direction of force? It is always directed toward the center of the Earth. We know that we get more acceleration as the direction of motion gets closer to the direction of force. Because we get motion even when the direction of motion is not exactly lined up with the direction of force there must be at least part of the force in the direction of motion.

Experiment II

Goal: To illustrate balance of force in the context of of gravity and vector decomposition.

Equipment: 1x Air Track, 2x stop watch, 1x protractor, graphing paper, pencils, string (4 meters), weights (1x, 2x, 3x)

Method: Set the air track so that one end is just at the end of a table. Tie one end of the string onto the air track cart and tie the other end to an identical mass that will drape over the air track such that it will hang off the elevated side (nearest the end of the table). Attach a mass to the air track cart of approximately 1.2 - 1.5 x a similar mass attached to the hanging cart. Starting the air track cart at a reasonable point along the track, elevate the table end of the air track to 10 degrees and record how long it takes for the air track cart to reach the elevated end (or some other prescribed point) by letting the hanging mass fall. Take 3-4 more measurements at increasing angles (5-10 degrees each time) but not so steep as to cause EQ or reverse the direction of motion (the track cart will always be heavier so at big angle it will dominate). Chart the initial measurements on a graph with angle on the independent (horizontal) axis and time on the dependent (vertical) axis; all points should lay within the first quadrant. From this make a prediction via regression to estimate the angle at which the time will be infinite -- the vertical asymptote; more data may need to be collected before this will readily be apparent. Try this angle to check the prediction.

Discussion: