Hour: ______ Date: __________________ Name: _________________________________________
Unit 5: Unbalanced Force (Net Force) Particle Model
Lab: Rocket Sled
Getting Ready
Navigate to the Rocket Sledder Interactive at TPC (http://www.physicsclassroom.com).
https://www.physicsclassroom.com/Physics-Interactives/Newtons-Laws/Rocket-Sledder
Click/tap the Launch Interactive button. Resize the Interactive as desired.
Explore
Use the Interactive to explore the following questions:
1. With Friction and Air Drag turned off, move the slider
right to apply a force in the positive direction.
F norm
Draw the force diagram. Label the forces using Fapp for
Applied force, Fnorm for Normal force from the ground,
and Fgrav for the Weight of the sled.
F app
Describe the effect that an applied force has upon the
velocity?
The applied force increased the velocity and it constantly increased.
2. Now turn off the jets so that there are no horizontal
forces acting on the rocket sled.
F gray
F norm
Draw the force diagram at the right. Use the same labels
as before: Fnorm and Fgrav.
Describe how a moving rocket sled moves when there
are no horizontal forces.
It moves at a constant speed instead of constantly increasing.
F grav
3. Now stop the rocket sled without restarting the simulation or reloading the page. What do
you have to do to stop a rightward moving rocket sled?
You have to turn on the air force and add friction
4. Draw the force diagram for a rightward-moving rocket
sled that is slowing down to a stop. Use the labels Ffrict
for Friction force and Fair for Air Drag Force.
5. Can an object be moving to the right even though
there are no rightward forces acting upon the object?
Yes
No
F norm
f air
F frict
F grav
If you answer Yes, then describe the movement of the
object. (In terms of its speed and direction)
if the force is negative and fast it will move
If you answered No, then review Newton’s First Law.
6. Turn Friction and Air Drag off and try the following: Get the rocket sled moving to the right
until the speed-o-meter reaches the red zone. Then reverse the direction of the applied force
so that it is directed to the left.
Does the rocket sled immediately change direction? Yes
No
Explain your answer.
The sled has to slow all the way down before moving
7. Consider the two resistance forces in this diagram:
Friction Force (Ffrict) & Air Drag Force (Fair).
Do they ever act in the same direction as the object moves? Yes
Experiment for a while before you describe your answer below.
No
It depends on how strong the applied force is. If there isnt a lot they can but they are usually on the opposite side
8. Turn Air Drag off, turn Friction on.
Set the applied force to 100 N (right). Add weights until the sled stops accelerating.
a. How many total weights did it take for the sled to stop accelerating?
12
100 N
b. What does Ffrict = __________
Set the applied force to 150 N (right). Add weights until the sled stops accelerating.
c. How many total weights did it take for the sled to stop accelerating?
14
150 N
d. What does Ffrict = __________
Set the applied force to 200 N (right). Add weights until the sled stops accelerating.
e. How many total weights did it take for the sled to stop accelerating?
16
200 N
f. What does Ffrict = __________
If we could set the applied force to 250 N (right)
g. How many total weights would it take for the sled to stop accelerating?
18
250 N
h. What would Ffrict = __________
9. Turn Friction off, turn Air Drag on.
Set the applied force to 200 N (right). Wait for the sled to stop accelerating.
a. What is the maximum speed with the small parachute?
28
b. What is the maximum speed with the large parachute?
29
c. Why is there a maximum speed?
The parachutes can only drag so much.
Assessment:
Consider the force diagrams below for five different situations.
1. Which object(s) could be moving to the right at a constant speed? Explain why.
Object a
2. Which object(s) could be moving to the right and speeding up? Explain why.
Object b
3. Which object(s) could be moving to the right and slowing down? Explain why.
Object d
4. Which object(s) could be moving to the left and speeding up? Explain why.
Object e
5. Which object(s) could be moving to the left and slowing down? Explain why.
Object c
6. Which object(s) could be moving to the right? Explain why.
Object e
7. Which object(s) could be moving to the left? Explain why.
Object d