1. Go to the following website:https://phet.colorado.edu/en/simulations/forces-and-motion-basics
2. Click on the "Motion" option in the "Physics" menu on the left side of the web page.
3. Click on the "Forces and Motion: Basics" experiment icon to launch it.
4. Click on the "Play" button to launch the experiment file.
5. Double click on the "Acceleration" icon to launch it.

Part 1: Single-Object System

1. Select the "Forces", "Values", "Masses", "Speed", and "Acceleration" items in the top, right menu.
2. In the top, right menu, drag the friction slider all the way to the left and set it at the "None" position.
3. In the right menu, click on the "Pause" sign.
4. In the menu on the bottom, increase the applied force to10 N.
5. Calculate the theoretical accelerationaTheo=Fm, whereF=10 N, andm=50 Kg.
6. Turn on the stopwatch on your phone and, simultaneously, click on the "Play" sign in the right menu. The box will start to accelerate as indicated by the increased speed on the speed gauge.
7. Wait until the box's speed reaches20 m/s, then simultaneously click on both the "Pause" sign in the right menu and the "Stop" sign on your stopwatch. Record the time readingt on your stopwatch.
8. Calculate the experimental acceleration according toaExp=vf-vi/t; note thatvf=20 m/s,vi=0 m/s, andt is the time reading on your stopwatch.
9. Compare the theoretical value fora obtained in (11) to the experimental value obtained in (14), then calculate the error percentage according to: Error Percentage =Theo. -Exp.Theo.100%.

Part 2: Multi-Object System

1. Start over by clicking on the orange button in the right menu.
2. Select the "Forces", "Values", "Masses", "Speed", and "Acceleration" items in the top, right menu.
3. In the top, right menu, drag the friction slider all the way to the left and set it at the "None" position.
4. Place the 100-Kg water container on top of the 50-Kg box by clicking on and dragging it from the bottom, right menu.
5. In the right menu, click on the "Pause" sign.
6. In the menu on the bottom, increase the applied force to10 N.
7. Calculate the theoretical accelerationaTheo=FmBox+mContainer, whereF=10 N,mBox=50 Kg, andmContainer=100 Kg.
8. Turn on the stopwatch on your phone and, simultaneously, click on the "Play" sign in the right menu. The box will start to accelerate as indicated by the increased speed on the speed gauge.
9. Wait until the speed reaches20 m/s, then simultaneously click on both the "Pause" sign in the right menu and the "Stop" sign on your stopwatch. Record the time readingt on your stopwatch.
10. Calculate the experimental acceleration according toaExp=vf-vi/t; note thatvf=20 m/s,vi=0 m/s, andt is the time reading on your stopwatch.
11. Compare the theoretical value fora obtained in (22) to the experimental value obtained in (25), then calculate the error percentage.