Forces of Friction
CHALLENGE (HYPOTHESIS) QUESTIONS
How do the different types of friction each work to impede motion of an object?
MATERIALS
1.
2.
3.
Friction Block with painted side
Force Meter (Spring Scale)
Wheeled Carts
4.
5.
Block Wrapped in Plastic
Mineral Oil
PROCEDURE
Part I: Static Friction
Directions
1. Attach the force meter to the block.
2. Pull gently on the force meter and record the reading (Newtons) JUST BEFORE the block begins to move.
(This number is equal to the static friction between the block and the table!)
3. Repeat 4 times and record in your science notebook.
Part II: Sliding Friction
Directions
1. Gently pull the block so it is moving at a slow, steady pace across your desk.
2. Record the reading on the force meter as the block is moving.
3. Repeat 4 times and record in your science notebook.
Part III: Rolling Friction
Directions
1.
2.
3.
4.
Balance the block on the Lego wheels
Gently pull the block so it is moving at a slow, steady pace across your desk.
Record the reading on the force meter as the block is moving.
Repeat 4 times and record in your science notebook.
Part IV: Fluid Friction
Directions
1.
2.
3.
4.
5.
6.
7.
8.
Use the block wrapped in plastic on a dry, clean countertop first.
Gently pull the block so it is moving at a slow, steady pace across your desk.
Record the reading on the force meter as the block is moving under “Fluid Friction Control”
Repeat 4 times and record in your science notebook.
Now use the block wrapped in plastic on the oiled surface.
Gently pull the block so it is moving at a slow, steady pace across your desk.
Record the reading on the force meter as the block is moving under “Fluid Friction Oiled Surface”
Repeat 4 times and record in your science notebook.
DATA OBSERVATIONS
Table 1: Comparing Static, Sliding, and Rolling Friction of the Block
Trial 1
Trial 2
Trial 3
Part 1- Static
Friction
Part 2- Sliding
Friction
Part 3- Rolling
Friction
Table 2: Fluid Friction
Fluid Friction
Part 4- Control
Trial 1
Trial 2
Trial 3
Trial 4
Average
Trial 4
Average
Part 2- Oiled
ANALYSIS
1.
2.
3.
4.
5.
6.
What happened to the reading on the force meter in Part 1 when the block first started to move? What does this
tell you about sliding friction vs. static friction?
Compare your results from Parts 1, 2, and 3. Which type of friction creates the least resistance to motion? Explain
your answer using data (NUMBERS!) from the experiment.
2
If the mass of the block was 0.3 kilograms, what force would be needed to accelerate it to 6 m/s ? Show your
work.
Describe the differences in the motion of the block in the control and the oiled surface in Part 4.
Predict what would happen to the reading on the force meter if we dragged the block along the carpet in the
media center. Why would this situation be different from sliding the block across a desk in the classroom?
Using a Full page in your Notebook, complete the following Four Square for an Additional Stamp.
FRICTION REVIEW – PG 380 – 383
STATIC FRICTION – PG 380 – 383
1.
What is Friction?
1.
Is there Friction between objects that are not moving?
2.
How does the direction of Friction compare to the
direction of motion?
2.
If you push on a desk and it does not move, what can you
conclude about static friction force?
3.
What determines the strength of friction?
3.
Describe a situation where static friction is helpful?
4.
Which has more friction, a tile floor or a carpeted floor?
Explain your answer.
4.
Draw a situation where static friction is NOT helpful.
FRICTION IN MOVING OBJECTS – PAGE 380 – 383
ELASTIC FORCES – PAGE 383
1.
Compare the strength of sliding versus rolling friction?
1.
What does “elastic” mean?
2.
Why is fluid friction usually low?
2.
What is compression?
3.
Compare the force needed to move the wooden block
when it was sliding compared to when it was on
wheels.
3.
What is tension?
4.
Describe what happens to a ball as it bounces. How is this an
example of elastic forces?
4.
Draw the force diagrams for the blocks on wheels and
when sliding. Label the direction of motion and the
direction of the force of friction.