Download Applied Force Weight Friction Normal Force Friction Activity

Friction Activity
Newton’s Second Law
Intro Physics
Name___________________________
Date____________________Hr.______
Introduction:
The force of friction between two surfaces is due to
microscopic bumps and ridges that prevent the object from
sliding smoothly. The force of friction is due to the size of
these bumps and ridges as well as the weight of the object.
To calculate the coefficient of friction between two surfaces,
you must divide the friction force by the normal force.
Normal
Force
Friction
Applied
Force
Weight
Purpose:
To identify the relationship between friction force and mass
on a wood block and to calculate the coefficient of friction
between a wood block and a wood board.
Hypothesis: circle one
Increasing the mass on a block of wood will (increase, decrease or not affect) the force of friction on
the block.
Materials
¾ 1 wood block
¾ 1 wood plank
¾ 3-500 gram masses
¾ Newton force scale
Procedure:
1. Weigh the wood block by hanging it from the Newton scale. Record in the table
2. Attach the Newton scale to the hook on the wood block. Pull on the scale until the block just
begins to move. Repeat with the same weight three times and calculate an average. Record
this average for one trial in the applied force section of the static friction column of the table
below.
3. For trial 2, add 0.5kg to the block and repeat step 2. For trial 3, add another 0.5 kg and repeat
step 2. For trial 4, add another 0.5kg and repeat step 2.
4. Remove all of the weights
5. Drag the block along the wood plank at CONSTANT VELOCITY. Repeat with the same
weight three times and calculate an average. Record this average for one trial in the applied
force section of the kinetic friction column of the table below.
6. For trial 2, add 0.5kg to the block and repeat step 2. For trial 3, add another 0.5 kg and repeat
step 2. For trial 4, add another 0.5kg and repeat step 2.
7. Make an Excel graph of Friction Force ( F f ) vs. Normal Force ( N ) and use the slope of this
graph to find the coefficient of static and kinetic friction.
Data: (type in final copy)
Trial
Static Friction
Average
Total Weight
Applied Force
W
FA
Kinetic Friction
Average
Total Weight
Applied Force
W
FA
1
2
3
4
Results: (make a graph in excel)
Using equilibrium, it is found that the normal force equals the force due to gravity (weight) and the
force of kinetic and static friction equals the force applied. The slope of force of friction vs. the
normal force graph will determine the coefficient of friction for both values.
Static Friction Force (N)
Coefficient of Static Friction
y = 0.2742x + 0.0374
6.0
5.0
4.0
3.0
2.0
1.0
0.0
0.0
2.0
4.0
6.0
8.0 10.0 12.0 14.0 16.0 18.0 20.0
Normal Force (N)
Kinetic Friction Force
(N)
Coefficient of Kinetic Friction
y = 0.1925x - 0.0897
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0
Normal Force (N)
Conclusion: (Change the underlined words and blank spaces to fit your data. Keep them bold and
underlined)
The purpose of this experiment was to identify a relationship between the friction force and weight of
a wood block and wood board and to calculate the coefficient static and kinetic friction between a
wood block and a wood board. It was stated in the hypothesis that increasing mass to the block will
(increase/decrease/not affect) the force of kinetic and static friction on the block. The hypothesis is
proved to be (correct/incorrect). The graph shows when the mass on a block is increased, the
friction force (is increased/is decreased/remains constant) In the first part of this experiment, a
random block was pulled with a constant force until the block began to move. Three trials were done
with four separate weights to determine the coefficient of kinetic friction. When graphing the
average friction force vs. normal force, it was determined by the slope that the coefficient of static
friction is 0.27. In the second part of this experiment, a random block was pulled with a constant
force to keep the block moving at constant velocity. Three trials were done with four separate
weights to determine the coefficient of kinetic friction. When graphing the average friction force vs.
normal force, it was determined by the slope that the coefficient of kinetic friction is 0.19.
When provided an electronic force sensor, an electronic graph printout of applied force vs. time was
produced (see attached). The actual kinetic coefficient was determined to be____ and static
coefficient was_____. The percent error for each was _____ and ______ respectively. There are
several sources of experimental error in this experiment. First, the smallest division on the scale was
______ giving a sufficient measurement uncertainty. Second, the procedure asks to drag the block at
constant speed but does not specify how to maintain a constant speed without a __________. Third,
the wood block and the wood board surfaces that were provided were not ___________. This will
cause different forces of static and kinetic friction as the block slides across the board. To improve
the experimental error in this experiment, the procedure could provide a ____________ scale, a
______________ to ensure the block is pulled at constant velocity and a ______________ board to
ensure that static and kinetic friction is constant.
Questions:
1. Does the weight of the block have an effect on the coefficient of friction?
2. Does dragging speed have an effect on the coefficient of kinetic friction?
3. How does the coefficient of static friction compare with the coefficient of kinetic friction at
each weight?
4. If the block were dragged on the edge, would this change the coefficient of friction?
Why/why not?