PhET Activity for MS-PS2-2: Forces and Motion_Basics

DIRECTIONS:
1. You are currently on the Main Menu.
2. Click on the 'Net Force' module button to begin.
3. Notice the blue and red figures at the bottom of the screen. These represent forces.
4. Observe the cart in the middle of the rope.
5. Locate the checkboxes for 'Sum of Forces', 'Values', and 'Speed' in the top right panel.
6. Find the 'Go!' button below the cart and the orange 'Reset' button in the top right.
Spend 2-3 minutes exploring the 'Net Force' module. Drag different figures onto the rope. Check and uncheck the boxes in the top right panel to see what information they show. Don't press 'Go!' just yet. Get comfortable with the setup.

QUESTION: Are you acquainted with the tools in this simulation?

DIRECTIONS:
1. If you have any figures on the rope, click the orange 'Reset' button in the top right corner.
2. Drag the largest blue figure onto the left side of the rope.
3. Drag the largest red figure onto the right side of the rope.
4. Check the boxes for 'Sum of Forces' and 'Values' in the top right panel.

QUESTION: When equal forces are applied to the cart in opposite directions, what is the 'Sum of Forces' (or net force)?

DIRECTIONS:
1. Ensure you have the setup from the previous slide (one large blue figure vs. one large red figure, with 'Sum of Forces' and 'Values' checked).
2. Check the 'Speed' box in the top right panel to show the speedometer.
3. Click the 'Go!' button.

QUESTION: When the net force on the cart is zero, its motion (a)   .

DIRECTIONS:
1. After the previous run, a 'Return' button should be visible. Click it.
2. If not, click the orange 'Reset' button. Then recheck the 'Sum of Forces' and 'Values' box in the top right panel.
3. Drag the largest blue figure (150 N) and the medium blue figure (100 N) to the left side of the rope.
4. Drag the largest red figure (150 N) to the right side of the rope.
5. Make sure the 'Sum of Forces' and 'Values' boxes are still checked.

QUESTION: The total force from the blue team is ___ N. The total force from the red team is ___ N. Therefore, the sum of the forces is ___ N to the left.

(a)  

DIRECTIONS:
1. Ensure you have the unbalanced setup from the previous slide (250 N left vs. 150 N right).
2. Make sure the 'Speed' box is checked.
3. Click the 'Go!' button.

QUESTION: What happens to the cart when the forces are unbalanced?

DIRECTIONS:
1. Click the orange 'Reset' button in the top right corner to reset the 'Net Force' module.
2. Click the 'Motion' tab at the bottom of the screen.
3. Check all the boxes in the top right panel: 'Force', 'Values', 'Masses', and 'Speed'.

QUESTION: In this 'Motion' module, what do you think is the independent variable (the thing you directly control) and what is the dependent variable (the thing that changes as a result)?

DIRECTIONS:
1. If there is anything on the skateboard, click the orange 'Reset' button.
2. Ensure you are on the 'Motion' tab with all display boxes checked.
4. Using the slider at the bottom, apply a force of 100 N to the right.

QUESTION: When a constant, unbalanced force is applied to the crate, its speed (a)   .

DIRECTIONS:
1. Click the orange 'Reset' button.
2. Make sure you are on the 'Motion' tab with all display boxes checked.
3. Remove the 50 kg crate from the skateboard. Drag the 200 kg refrigerator onto the skateboard.
4. Using the slider at the bottom, apply the same force as before: 100 N to the right.

QUESTION: With the same applied force, how does the change in speed of the 200 kg refrigerator compare to the change in speed of the 50 kg crate?

DIRECTIONS:
1. Click the orange 'Reset' button and recheck the boxes in the top right panel.
2. Place the 50 kg crate on the skateboard.
3. Apply any force until the speed reaches roughly 15.0 m/s.
4. As soon as the speed is 15.0 m/s, remove the 'Applied Force' so that the slider is back to 0 N.

QUESTION: In the 'Motion' tab (with no friction), once an object is moving, if the applied force is removed the net force becomes ___ N and the object moves at a ___ velocity.

(a)  

DIRECTIONS:
1. Click the 'Friction' tab at the bottom of the screen.
2. Check all the boxes in the top right panel: 'Force', 'Sum of Forces', 'Values', 'Masses', and 'Speed'.
3. Notice the new 'Friction' slider in the panel.

4. 4. Experiment with the applied force to make the crate move and stop.
   
   QUESTION: Arrange the following actions into the correct order to test how friction stops a moving object.