2.1

Constant Velocity Versus Constant Acceleration

Student Notes

Two balls are shown on your screen. Both will move to the right when you start the simulation. The upper ball moves with a constant velocity of 5 m/s. The lower ball starts from rest, but moves with constant acceleration. You can set the lower ball's acceleration using a slider. The simulation stops when one ball reaches the right side of the screen. Graphs of position and velocity vs. time are shown for each ball.
Run the simulation with the default value of acceleration (1 m/s2).

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Describe the motion of the two balls in words.
What is "constant" about the motion of the lower ball?
If the acceleration of the lower ball is doubled, what will happen to the motion? Make a prediction by sketching new graphs for the position and velocity vs. time, then set the new acceleration. Run the simulation to check your prediction.

Self-test

Suppose the acceleration is set so that the ball with constant acceleration makes it to the finish line at the same time as the ball that moves with constant velocity. What special relationship do their average speeds have?
Suppose the acceleration is set so that the ball with constant acceleration makes it to the finish line at the same time as the ball that moves with constant velocity. Where is the lower (constant-acceleration) ball when the upper ball is half way to the finish?

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