# Free Fall Simulation - Initial Upward Velocity

## Discussion:

In this activity, you will use the Interactive PhysicsTM program to simulate the motion of a ball in free fallwith an initial upward velocity. When you first load the simulation file, it is set up to simulate tossing a ball near the surface of the Earth, where g = 10 m/s2 (approximately). After investigating this motion, you will alter the value of g to simulate tossing a ball on the Moon, where g = 1.63 m/s2.

# Procedure:

1. Double-click on the file "ip_free_fall_2_sim" which you will find in your "Group Shared" folder. This will start the Interactive PhysicsTM software and load the free fall simulation. (Interactive PhysicsTM software may not be available on all computers.)
2. This simulation is much like the "free fall from rest" simulation, except that you can use the slider to set the initial upward velocity of the ball. The allowed range for this velocity is 0 - 40 m/s.
3. Set the initial velocity, and click "Run" on the toolbar. The ball will begin to move. Notice how the position, velocity, and acceleration meters change as the ball moves. To stop the simulation, click "Stop" (the "Run" button changes to a stop sign while the simulation is running.). Note that you can start and stop the simulation by alternately clicking "Run" and "Stop". To reset the simulation, click the "Reset" button.
4. Now, construct a data table in which you can record the position, velocity, and acceleration for the ball for each second from 0 seconds until it returns to its original position. (You may use any initial velocity that you wish, but a multiple of 10 m/s will make for easier calculations.)
5. Reset the simulation and click "Run". When the timer is near 1 second, click "Stop". Use the frame advance buttons to move the timer to precisely 1 second, and enter the data for position, velocity, and acceleration in your data table. Click "Run" again, and stop the simulation and record your data for the next second, etc.
6. Repeat steps 4 and 5 for a different initial velocity.
7. Change the free fall acceleration to approximate gravity on the moon (about 1.630 m/s2) and repeat steps 4 and 5 for tossing a ball on the moon.

## Questions:

1. As the ball moves, what happens to its velocity? (Remember that a quantitative description is superior to a qualitative description...)
2. As the ball moves, what happens to its acceleration?
3. Suppose that you toss a ball upward on Earth and then toss the same ball upward with the same initial velocity on the Moon. How do the motions compare? (How is it the same, and how is it different?)
4. For one of you simulated ball tosses on Earth, calculate the velocity and position of the ball for each second that it was in the air. Be sure to show your neat, complete calculations. Compare your calculated results with the simulation results.
5. For the other simulated ball toss on Earth, calculate the maximum height of the ball and the time that the ball will be in the air. Be sure to show your neat, complete calculations. Compare your calculated results with the simulation results.
6. For the simulated ball toss on the Moon, calculate the maximum height of the ball and the time that the ball will be in flight. Be sure to show your neat, complete calculations. Compare your calculated results with the simulation results.

last update October 4, 2001 by JL Stanbrough