Name____________________________________________Grade____________________________________________

Forces and Motion Pre Lab

Joe needs to push a file cabinet across the room. He begins by just looking at it. (Scene 1) He then begins pushing on the file cabinet. At first, the file cabinet does not move. (Scene 2) Then the file cabinet begins to slide. (Scene 3)

a. Use words and pictures to describe all the forces you think are acting on the cabinet in each scene.

b. Why do you think the file cabinet moves (accelerates from zero) in scene 3 but not in scene 1 or 2?

Forces and Motion

Scene 1:Joe not pushing

Scene 2:Joe pushing but cabinet not

moving

Scene 3:Joe pushing and cabinet

moving

1

c. If the floor is covered with ice, how would the motion of the cabinet change?

Forces and Motion 2

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Forces and Motion 3

Name____________________________________________

Forces and MotionLearning Objectives:

Be able to identify when an object is being acted upon by unbalanced forces. Be able to predict the change in motion when a force is applied to an object.

Go to the PhET Website (just google PhET to get there). Go to the simulations, click on “physics” and find the “Forces in 1-Dimension” simulation (it may take a few moments to load).

Part 1: Understanding balanced and unbalanced forces

Open the Forces and Motion Simulation by clicking the icon on your computer’s screen.1. What do you observe about applied force and motion?

2. What do you observe about friction force and motion?

3. Using the simulation for help, we drew pictures showing Joe and the file cabinet.Draw the force vectors on the file cabinet in each scene. Label them Balanced or

unbalanced.Scene 1:

Joe not pushingScene 2:

Joe pushing but cabinet not moving

Scene 3:Joe pushing and cabinet moving

4. What happens to the applied force when Joe stops pushing on the cabinet?

5. Can the object still move, once Joe stops pushing?

Forces and Motion 4

Part 2: Understanding Applied, Friction and Total Force

6. Apply enough force to move the cabinet.

a. What happens to the Friction Force when you stop applying force?

b. What happens to the Friction Force once the cabinet stops moving?

Part 3: Graphing

Click on , and to show the graphs of motion. To go back to the

main screen, you click the X in the right corner of the graph.

Remember…it is not the presence of forces that cause acceleration…it is the presence of unbalanced or NET forces!

A. Set the “Initial Position” to -2 m. the simulation between runs to reset the simulation.

B. Have Joe push the cabinet until it begins to move, then have him stop pushing completely.

Draw a sketch of the velocity, and position graphs produced.

Velocity vs time Position vs time

Forces and Motion 5

Name____________________________________________Grade____________________________________________

Forces and Motion Homework1. Joe needs to push a file cabinet across the room. He begins by just looking at it. (Scene 1) He then begins pushing on the file cabinet. At first, the file cabinet does not move. (Scene 2) Then the file cabinet begins to slide. (Scene 3)

a. Use words and pictures to describe all the forces you think are acting on the cabinet in each scene.

b. Why do you think the file cabinet moves in scene 3 but not in scene 1 or 2?

c. What do you think Joe could do to make the cabinet move faster?

Forces and Motion

Scene 1:Joe not pushing

Scene 2:Joe pushing but cabinet not

moving

Scene 3:Joe pushing and cabinet

moving

6

d. If the floor is covered with ice, how would the motion of the cabinet change?

e. What would be different if Joe was moving a book, instead of a file cabinet.

2. How useful for your learning was this science activity, compared to other science class activities? (circle)

More useful About the same Less useful

How enjoyable was this science class activity, compared to other science class activities? (circle)

More enjoyable About the same Less enjoyable

Why did you or did you not find it useful or enjoyable? ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Conclusion Questions:

1. As a small force was applied to the cabinet, the cabinet didn’t move because the magnitude of the force of

friction was larger than / smaller than / equal to the applied force. BE CAREFUL HERE

2. Our experiment showed that static (not moving) friction is greater than / less than kinetic (moving) friction.

3. I’m not accelerating, so the net (vertical) force on me, while I’m sitting here doing this lab is _________.

4. Without friction , applying a constant force produces a decreasing / constant / increasing acceleration.

5. Without friction , applying a constant force produces a decreasing / constant / increasing speed.

6. While coasting (no applied force) without friction, the acceleration is __________ and velocity is ________________.

14. Write 1.)Which direction you think the object is moving. 2.) Will it speed up or slow down. 3.) Why?

a.

b.

Forces and Motion 7

c.

Forces and Motion 8