Name
Hour
You are able to earn 30
summative points on
this lab. That means it
is like a quiz or a test.
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Lab: Friction
Prelab
Directions: While viewing the Friction PowerPoint fill in the following answers.
What is friction?
What would happen if there were no friction?
Draw a Free-Body diagram, in the box to the right,
showing friction and some type of force. Be sure to
label them correctly and with arrows.
Friction is a force like any other force and affects
motion. Friction occurs in…
a) solids sliding over one another.
b) fluids.
c) air.
d) all of these.
Two forces act on a book resting on a table: its weight and the support force from the table. Does a
force of friction act as well?
Explain
Part I: Air Friction
The first kind of friction you will be investigating is air friction. You will begin by finding out how the car moves
before you add extra air friction.
1. Set up the track as a long straight hill as
shown above.
2. Attach the track to the stand at the seventh
hole from the bottom.
Time from A to B
3. Place one photogate near
the top of the track and
one near the bottom of
the track so they are 60cm apart.
4. Set up the Labquest device like in previous
labs.
5. Use the Labquest device to collect data for
Table 1.
Rolling Car without a sail: Measuring Air Friction of a Rolling Car Without a Sail.
 Before you start your trials be sure to put a steel ball in the middle pocket of the car.
Table 1: Rolling Car without a Sail
Trial
Distance between A and B (cm)
1
60 cm
2
60 cm
3
60 cm
Time from A to B (sec)
Speed from A to B (cm/s)
(Calculate using Distance÷Time)
Average Speed of 3 trials
Rolling Car with a sail
Measuring Air Friction with a “Sail Car”.
The sail car should look like the picture
to the right.
Your Hypothesis: Write a hypothesis that compares the speeds of the “sail car” and the normal car. Write
your hypothesis using the following format.
IF
THEN
BECAUSE
Explain the reasoning behind your hypothesis.
Repeat the first part of the lab with the provided “Small Sail Car” – car with small paper plate. MAKE SURE TO
USE THE STEEL BALL IN THE CAR and that the PLATE IS FACING DOWN THE TRACK!
Table 1 : Small Sail Car – Small paper plate
Trial
Distance between A and B (cm)
1
60 cm
2
60 cm
3
60 cm
Time from A to B (sec)
Average Speed of 3 trials
Speed from A to B (cm/s)
(Calculate using Distance÷Time)
Stop and Think
1. Did your results confirm your hypothesis?
Explain.
2. How did air friction affect the car’s motion?
Apply what you learned
1. Friction is a force that opposes motion. Explain where the friction force on the sail comes from.
2. How could you increase the air friction on the car?
3. How could you decrease it?
4. Is the sail the only source of friction?
Explain
Repeat again using the “Large Sail Car.” (car with larger paper plate attached). MAKE SURE TO USE THE STEEL
BALL IN THE CAR!
Table 2 - Large Sail Car – Larger paper plate
Trial
Distance between A and B (cm)
1
60 cm
2
60 cm
3
60 cm
Time from A to B (sec)
Speed from A to B (cm/s) (Calculate
using Distance÷Time)
Average Speed of 3 trials
5. How did the large sail car compare to the small sail car?
This is the end of part I. You can
here. We will do the rest later
Part 2: Rolling, Sliding, and Air Friction
1. Set up the track so it is level, you will not be using the vertical stand. Put a rubber band on the
end of the track opposite of the clay. As you attach it, twist it once so it makes an X. You will be
using the rubber band to launch the car and sled.
2. Adjust the starting peg so it is approximately 4cm from the rubber band.
3. Place the sled (car without wheels) on the track so the nose of it is touching the rubber band.
4. Put the metal ball in the sled.
5. Move the top photogate to the 25 cm mark and then move the bottom photogate so it is at the
70cm mark.
6. Launch the sled by pulling the rubber
band back and under the screw head.
Then press down on the rubber band
with a pen/pencil/finger. Practice a
few times before you start recording
data. Like the pictures to the right. You
could also try twisting the screw to
release the rubber band.
7. The sled should make it through both
photogates. If it stops too soon, keep
practicing, or adjust the stopper so
you can pull the sled back a little
farther.
8. COLLECT ALL DATA (Columns 1 -3) BEFORE DOING THE CALCULATIONS!!!!!
Total Time
Time from A to B
Time through A
Use the Labquest Device to collect data for Table 4, 5, and 6.
a. Time through A = Look at picture above. (Column 1)
b. Time from A to B = Look at picture above. (Column 2)
c. Total Time = Look at picture above. (Column 3)
DURING DATA COLLECTION:
Collect these three pieces of
data for each sled/car.
d. Time through B = Total time – Time from A to B (Column 3 – Column 2)
e. Speed at A = 1cm ÷ time through A
(1cm ÷ Column 1)
Speed at B = 1cm ÷ time through B
(1cm ÷ Column 4)
f.
g. Acceleration = Speed B – Speed A ÷ Average time from A to B
(Column 6 – Column 5) ÷ Column 2
AFTER DATA
COLLECTION:
Use the data you
just collected to
do these
calculateion.
Table 3 - Sled
Trial
Column 1
Column 2
Column 3
Column 4
Column 5
Column 6
Column 7
Time
through A
(sec)
Time from
A to B
(sec)
Total
Time (sec)
Time
through B
(sec)
Speed at A
(cm/s)
Speed at B
(cm/s)
Acceleration
(cm/s2)
1
2
3
Average Acceleration
Repeat for both the rolling car, small sail car, and large sail car.
Table 4 - Rolling Car
Trial
Column 1
Column 2
Column 3
Column 4
Column 5
Column 6
Column 7
Time
through A
(sec)
Time from
A to B
(sec)
Total
Time (sec)
Time
through B
(sec)
Speed at A
(cm/s)
Speed at B
(cm/s)
Acceleration
(cm/s2)
1
2
3
Average Acceleration
Table 5 – Small Sail Car
Trial
Column 1
Column 2
Column 3
Column 4
Column 5
Column 6
Column 7
Time
through A
(sec)
Time from
A to B
(sec)
Total
Time (sec)
Time
through B
(sec)
Speed at A
(cm/s)
Speed at B
(cm/s)
Acceleration
(cm/s2)
1
2
3
Average Acceleration
Thinking about your data
1. Were your accelerations positive or negative?
Explain your answer
2. Which decelerated more, the sled or the car?
How do you know this?
3. What does your answer to the previous question tell you about the rolling friction of the car compared
to the sliding friction of the sled?
4. How could you increase the sliding friction between the sled and track?
5. How could you decrease the sliding friction between the sled and track?
6. How could you increase the rolling friction between the car and track?
7. How could you decrease the rolling friction between the car and track?
8. Compare rolling friction, air friction, and sliding friction by answering the following questions.
a. Which of the three types of friction that you tested do you think has the greatest effect on the
car’s/sled’s motion?
What evidence do you have from your data
that helps to support your answer?
b. Which of the three types of friction that you tested do you think has the least effect on the
car’s/sled’s motion?
What evidence do you have from your data that
helps to support your answer?
Turn this into the basket when you are done