# Free Fall

### (uses Interactive PhysicsTM)

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BHS -> Staff -> Mr. Stanbrough -> AP Physics -> Kinematics -> this page

Free fall is probably the easiest situation to simulate using the Interactive Physics program - all you do is create an object, and let it go!

## The Problem:

We will set up the simulation to solve the following problem:

A ball is dropped from rest and falls freely (no air resistance) for 4.0 seconds. How far will it fall it this time, and how fast will it be going after the 4.0 seconds has elapsed?

## The Simulation:

 Here is a screen shot of the starting state of the simulation.
 The Properties Window for this simulation.
To set up this simulation:

1. Open the Interactive Physics program.
2. You might want to resize the window to make it taller and thinner, but that's up to you.
3. Set the accuracy of the simulation to "Accurate".
4. You can change the acceleration of gravity to 10.0 m/s2 to make checking the simulation's results easier, if you wish, but check with your instructor first.
5. Create a new object - its size and shape doesn't matter.
6. Open your object's Properties Window and set:
1. x = 0.0
2. y = 0.0
3. vx = 0.0
4. vy = 0.0
7. Create a Time meter (clock).
8. Create a P-V-A meter (Y direction) for your object.
9. Add a velocity vector and an acceleration vector to your object.

Now, run the simulation. Watch the clock. When you get near 4.0 seconds, stop the simulation, and use the tape player controls at the bottom of the screen to get to 4.0 seconds exactly. Read the results from the P-V-A meter.

# Some Additional Problems:

In the following problems, air resistance is to be neglected.

1. What effect does changing the mass of the object have on the results of the simulation? Report your results.
2. What effect does changing the size (select and drag a corner with the mouse) of the object have on the results of the simulation? Report your results. (You can find the area of the object near the bottom of its Properties Window.)
3. An object is thrown downward with a speed of 5.0 m/s (vy = -5.0 m/s). How fast will it be going in 3.0 s? How far will it have fallen? How is this related to the speed and displacement it would have had if it had been released from rest? Explain your results.
4. A ball is thrown straignt upward with an initial speed of 15 m/s (vy = 15 m/s). Where will it be in 4.0 s, and what will be its velocity (speed and direction)?
5. A ball is thrown straight upward with a starting speed of 30 m/s. Make a data table and record its acceleration, velocity and position at 0.5 second intervals for 10.0 s. Construct acceleration vs. time, velocity vs. time, and position vs. time graphs for this motion. Use graph paper.

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BHS -> Staff -> Mr. Stanbrough -> AP Physics -> Kinematics -> this page
last update June 15, 2000 by JL Stanbrough