- How do the initial horizontal positions of the two balls compare? Are they at the same position, or is one ahead of the other?
- Do one or both of the balls pass each other? At what time does this happen? What is true about their horizontal positions when one passes the other? What is true about their relative velocities when one passes the other?
- Measure the position of the red ball at the beginning and two latter times. Use this information to calculate the initial velocity and acceleration of of the red ball.
- Write the equation of motion for the red ball in the box below. Your equation will look something like:

Then click on the button to make the blue ball follow your equation of motion. If the two balls do not move together, check you calculations of initial position, velocity and acceleration of the red ball.*x*+*v**t + 0.5**a**t^2

Exercise created by Scott Bonham, Western Kentucky University.

Physlet by Wolfgang Christian, Davidson College