LAB REPORT FOR M3 EXPERIMENT: EQUILIBRIUM OF
FORCES
VI1:
The main objective of this part of the lab was to establish the degree of sensitivity that was associated
with the apparatus we used to measure the forces. Essentially, we were finding the uncertainty (σ). We found
that in order to create a lack of equilibrium it took the addition of a minimum of 5.0 grams added to one of the
forces or a minimum adjustment of 2.0 degrees to any one of the angles of the forces. These values are recorded
below.
VI2:
In this section of the lab we set up the force table; first, with only 3 forces, 2 forces at 120° from each
other and varied the 3
rd
in an attempt to recreate equilibrium using different masses to adjust the other forces.
Then, with 4 forces, 3 forces were 90° from each other and then the 4
th
was varied while we added masses to
create equilibrium between the forces.
The table of these masses, forces, and angles are recorded in the table
below. To calculate force I used the equation
F
1
=m
1
g
where the force is equal to mass x gravity and the
units for mass are kg so the units for force are Newtons or kg/m/sec
2
.
Using 3 forces
1
2
3
m
1
(kg)
.150
.100
.125
Ø
1
(angle)
0°
0°
0°
Force
1
(kg/m/sec
2
)
1.47N
0.98N
1.225N
m
2
(kg)
.100
.145
.100
Ø
2
(angle)
120°
120°
120°
Force
2
(kg/m/sec
2
)
0.98N
1.421N
0.98N
m
3
(kg)
.140
.125
.115
Ø
3
(angle)
220°
255°
230°
Force
3
(kg/m/sec
2
)
1.372
N
1.225N
1.127N
VI3:
Each of the forces calculated in VI2 represent a vector, for example for Force
1
using only 3 forces the
vector is
F
1
. We can graphically represent the resultant vector of
F
1
+
F
1
as an arrow drawn from the end of
vector
F
2
to the beginning of vector
F
1
. This represents the “true” magnitude and direction of vector
F
3
. The
graphs of Trial 1 for both 3 forces and 4 forces are attached to the end of the lab report. For both graphs
1cm=0.1N
VI4:
For the graph of the 3 forces, the resultant vector appears to be about 0.9 cm which would equate to a
force of 0.09N, according to my calculations in VI5 the resultant vector should be 0.078N. Ideally the resultant
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 Fall '08
 SHI
 Physics, Force, Mass, resultant vector

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