Download Make-up #4

Name:
Physics
Date:
Forest Hills High School
Lab: Forces and Motion
Objectives:
1. Observe force and motion to explore the relationship between force, mass and acceleration
2. Investigate and determine the acceleration of an object.
Part I: Exploration
1. Go to: http://phet.colorado.edu/sims/html/forces-and-motion-basics/latest/forces-and-motionbasics_en.html. Click on motion (feel free to explore the simulation for a few minutes).
2. Select the Forces, Values, Masses, and Speed checkboxes in the yellow box on the top right.
3. Place the box on the skateboard. Set the applied force to 100N. Watch the speedometer as the box on
the skateboard picks up speed.
4. Now place the refrigerator on the skateboard. Set the applied force to 100N and watch the
speedometer as it picks up speed.
Analysis Questions:
1. What is the relationship between an object’s mass and its ability to accelerate?
2.
3.
4.
5.
What value do you think the wooden man and arrow represent? _______________________________
What value do you think the object on the skateboard represent? ______________________________
What value does the change in speed represent? ____________________________________________
Put the box and refrigerator on the skateboard and set the amount of applied force to 100N.
a. Predict if the acceleration will increase or decrease.
6. Reset the scenario and check off Forces, Values, Masses, and Speed on the top right. Put the box back
on the skateboard, but this time set the amount of force to 300N. Observe the motion of the box.
a. What is the relationship between the amount of applied force and an object’s ability to
accelerate?
Part II: Investigation: Newton’s Second Law (FNet=ma)
Part A: Constant with Varying Mass:
1. Set the force to 100 N and the mass to 40 kg. You will be increasing the mass in this section, while
keeping the force constant at 100 N.
2. Before increasing the mass in the simulation, predict what will happen to the acceleration as the mass
increases. Explain why you think this:
Prediction & Explanation:
Turn & Talk: Turn to your neighbor and share your predictions with one another.
a. How do your predictions compare?
b. Revisit your prediction. Have you changed your mind after speaking with your partner, or will you
keep your original prediction?
3. Now increase the mass starting at 40 kg, progressing towards 50 kg, 80 kg, 100 kg, and 200 kg. Then fill
in the chart and calculate the acceleration using Newton’s second law:
Table 1.
Mass (kilograms)
Force (Newtons)
Acceleration (m/s2)
40 kg
100 N
50 kg
100 N
80 kg
100 N
100 kg
100 N
200 kg
100 N
Analysis Questions:
1. What happened as you increased the mass?
2. Was your prediction correct? Explain.
Part B: Constant with Varying Force:
1. Set the mass to 100 kg and the applied force at 50 N.
2. Before increasing the intervals of force, predict what will happen as you increase the force:
Prediction & Explanation:
Turn & Talk: Turn to your neighbor and share your predictions with one another.
a. How do your predictions compare?
b. Revisit your prediction. Have you changed your mind after speaking with your partner, or will
you keep your original prediction?
3. Now slowly raise the applied force by intervals of 50 N. Fill in the chart and calculate the acceleration
using Newton’s second law:
Table 2.
Mass (kilograms)
Force (Newtons)
Acceleration (m/s2)
100 kg
50 N
100 kg
100 N
100 kg
150 N
100 kg
200 N
100 kg
250 N
Analysis Questions:
1. What do you notice about the relationship between force and acceleration? Explain.
2. Was your prediction correct? Explain.
Part III: Application
1. Use your knowledge of acceleration to find the mass and force by dragging different objects to your
skateboard and applying force.
2. Fill in the chart below:
Table 3.
Acceleration
Name of Object
Mass (kilograms)
Force (Newtons)
(m/s2)
1
2.2
2.5
4
6
Conclusion Question:
1. Explain the relationship between force, mass, and acceleration.
Further Thinking - Applying Friction:
Ms. Calabrese needs to push a filing cabinet across the room. She beings by looking at it (Scene 1), then
starts pushing on it. At first, it does not move (Scene 2). Then, after some pushing, it begins to slide (Scene
3).
Scene 1:
Ms. Calabrese is not
pushing
Scene 2:
Ms. Calabrese is pushing
but cabinet not moving
Scene 3:
Ms. Calabrese is pushing
and cabinet moving
2. Draw free body diagrams for each scene to illustrate all of the forces you think are acting on the
cabinet.
3. Why do you think the cabinet moves in Scene 3, but not in Scene 1 or Scene 2?
4. What do you think Ms. Calabrese could do to make the cabinet move faster?
5. If the floor is covered with ice, how would the motion of the cabinet change?
6. What would be different if Ms. Calabrese was pushing a book, instead of a cabinet?