NAME____________________________
BLOCK __________ DATE________________________
FORCES: SIMULATION LAB
Purpose:
How do balanced and unbalanced forces affect motion?
Materials:
Phet simulation -> Google: Phet Simulations -> “Forces and
Motion Basics” -> Run Now -> Update Later -> Run
http://phet.colorado.edu/en/simulation/forces-and-motionbasics
Directions:
Open the “Forces and Motion: Basics” program.
Click the “Friction” tab at the top.
In the box on the right, be sure the following boxes are selected: Forces, Sum of Forces, Values, Masses,
and Speed. – DO NOT CHANGE THE AMOUNT OF FRICTION
1. Where it says “Applied Force”, click the right arrow twice so it reads “100 Newtons”.
A. Describe the motion of the box. _________________________________________________
B. Why did the box do what it did? _________________________________________________
___________________________________________________________________________
C. Are the forces balanced or unbalanced? ______________________________
2. Increase the applied force to 150 Newtons.
D. What is the sum of forces? _____________
E. What happens to the speed of the box the longer the force is applied? _________________
F. Are the forces balanced or unbalanced? ______________________________
G. Draw a…
Force diagram
Motion diagram
3. Reduce the applied force back to 100 Newtons.
H. What happens to the sum of forces? _____________________________________
I. Are the forces balanced or unbalanced? _________________________
J. Describe the motion of the box ____________________________________
4. Increase the applied force to 200 Newtons. Once the box is moving quickly, add another 50 kg
box on top of the first one.
K. What happens to the sum of forces? ___________________________________
L. Why did the sum of forces change the way it did? __________________________________
___________________________________________________________________________
M. How did the speed change? ____________________________________________________
N. Predict what would happen if you changed the applied force to 250 Newtons. ___________
___________________________________________________________________________
5. Change the applied force to 250 Newtons.
O. What is the sum of forces? ____________________________________
P. Are the forces balanced or unbalanced? ______
Q. What happens to the speed of the boxes? ______________________________________
R. Draw a…
Force diagram
Motion diagram
S. What is the connection between balanced forces and velocity?
___________________________________________________________________________
___________________________________________________________________________
6. Increase the applied force to 500 Newtons. Press “Play” until the man cannot hold on any
longer.
T. What happens to the speed? _____________________
U. Once the man cannot hold on any longer, what happens to the Sum of Forces, Friction
Force, and Speed of the boxes? ______________________________________________
___________________________________________________________________________
7. Click “Reset”. Be sure to reselect Forces, Sum of Forces, Values, Masses, and Speed. Turn
Friction down to NONE. Increase the applied force to 100 Newtons. Press “Play”, then “Pause”
once you have seen what happens.
V. Why does the box move with only 100 Newtons of force when it didn’t before?
___________________________________________________________________________
8. Decrease the applied force to 0 Newtons.
W. Are the forces balanced or unbalanced? ______________________
X. What happens to the speed of the box? ____________________________________
9. Click the “Net Force” tab at the bottom. Turn off the Sound. Click on Values and Sum of Forces.
Place a small blue man on the left side and a small red man on the right side. Click “Go”.
Y. What happens to the Sum of Forces? ________________________________________
Z. Why did this happen? ________________________________________________________
___________________________________________________________________________
10. Now place another small blue man on the left and the largest
red man on the right. Click “Go”.
AA. What happens to the Sum of Forces?
____________________________________________
BB. Explain why the motion of the box changed the way it did.
___________________________
______________________________________________
11. Explain differences between balanced and unbalanced forces
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________
______________________________________________________________________________