1
Friction
We are attempting to observe the
frictional force of a 126.2 g block when acted on
by a rope attached to a weight hanging off a
pulley. Using a computer, we will analyze the
forces and velocity of the cart.
Exercise 1: Determining the Coefficient of Kinetic Friction between
Wood and Aluminum
Experiment:
We set up the cart as shown in the above diagram. We tried to keep the velocity
constant between .2 and .3 meters per second. As we added 100 g increments, up to 400
g, we added mass to the hanging weight to increase velocity to the desired range.
Data:
The following is the recorded data from exercise 1.
Exercise 1
Mass (kg)
Normal Force (N)
Hanging Mass (kg)
Hanging Force (N)
0.1262
1.23676
0.03
0.294
0.2262
2.21676
0.054
0.5292
0.3262
3.19676
0.085
0.833
0.4262
4.17676
0.105
1.029
0.5262
5.15676
0.13
1.274
The above normal force was calculated as equivalent to the weight of the block,
since the track was horizontal.
n = W = 9.8 m/s
2
x m
Ex: n = W = 9.8
m/s
2
x .1262 kg = 1.23676 N
The hanging force was calculated by the following equation:
W = 9.8 m/s
2
x m
Ex: W = 9.8
m/s
2
x .03 kg = .294 N
To determine the magnitude of the frictional force acting on the block, the
relationship between the normal force and the force required to move the block must be
found. This was found by graphing the hanging force as a function of the normal force.
The two forces are related by the following linear equation:
F
h
= 0.251F
n
 0.0105
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The slope of the equation gives us our kinetic friction coefficient:
μ
k
= .251
Exercise 2: Checking Whether Velocity Affects the Frictional Force
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 Fall '06
 Cerruti
 Physics, Force, Friction, Mass, Velocity, 125 kg

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