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7. Sample Experiments
To
make
time
measurements
instruments are recommended:
1 Mechanical stopwatch
or
1 Laser reflection sensor
and
1 Digital counter (230 V, 50/60 Hz)
or
1 Digital counter (115 V, 50/60 Hz)
7.1 Uniformly accelerated rotation
7.1.1 Making a graph of rotation angle versus time
Recommended parameters:
Accelerating mass m
= 2 g
M
Multiple pulley radius r
Additional weight m
= 25 g, distance r
J
Rotation angles ϕ = 10°, 40°, 90°, 160°, 250°
•
Slide the two additional weights onto the
transverse beam at the same distance from the
axis of rotation.
•
Attach a thread to the metal peg on the rotating
disc and wind about 5-6 turns around a groove of
the multiple pulley.
•
Run the other end of the thread over the pulley
and tie one of the S-shaped hooks firmly onto the
end.
•
Position the system so that the S-shaped hook
hangs over an edge of the work-bench.
•
Turn the rotating disc to the desired angle
position and restrain it with the pointer.
•
Switch on the compressor.
•
Press the lever down to start the rotation, and
simultaneously start the stopwatch for the time
measurement.
•
When the zero mark passes the position of the
pointer, stop the time measurement, read the
time, and write it down.
•
Determine the times for different angles of
rotation and plot a t -
For the parameters recommended above, the times
are as follows:
10°
40°
2 s
4 s
7.2 Angular acceleration as a function of torque
7.2.1 Angular acceleration with different accelerating
masses
Recommended parameters:
ϕ
Angle of rotation
= 90°
the
following
U40801
U8533380
U8533341-230
U8533341-115
= 10 mm
M
= 170 mm
J
ϕ
diagram.
90°
160°
6 s
8
Additional weight m
Multiple pulley radius r
Accelerating masses m
•
Set up the experiment as described under 6.1.
•
Determine the times for the same angle of
rotation with different accelerator masses m
calculate the corresponding angular accelerations
α
.
•
Display
acceleration
diagram.
7.2.2 Angular acceleration with different multiple
pulley radius
Recommended parameters:
Angle of rotation
Additional weight m
Accelerating mass m
Multiple pulley radii r
•
Set up the experiment as described under 6.1.
•
Determine the times for the same angle of
rotation with differing pulley radii r
calculate the corresponding angular accelerations
α
.
•
Display the dependence of the angular
acceleration
pulley r
7.3 Angular acceleration as a function of the
moment of inertia
7.3.1 Moment of inertia as a function of the additional
weight
Recommended parameters:
Angle of rotation
Accelerating mass m
Multiple pulley radius r
Distance r
= 210 mm
J
Additional weights m
•
Set up the experiment as described under 6.1.
•
Determine the times for the same angle of
rotation with different additional masses m
the
same
250°
corresponding moments of inertia J using
Equations 4, 5 and 1.
10 s
•
Display the dependence of the moment of inertia
J on the additional mass m
7.3.2 Moment of inertia as a function of the distance
of the additional masses from the axis of rotation
Recommended parameters:
angle of rotation
accelerator mass m
4
= 50 g, distance r
J
= 10 mm
M
= 1 g, 2 g, 3 g, 4 g
M
the
dependence
α
on the accelerator mass in an
ϕ
= 90°
= 50 g, distance r
J
= 2 g
M
= 5 mm, 10 mm, 15 mm
M
α
on the radius of the multiple
α
in an r
-
diagram.
M
M
ϕ
= 90°
= 2 g
M
= 10 mm
M
= 0 g, 12.5 g, 25 g, 50 g
J
distance
r
,
and
J
in an m
J
ϕ
= 90°
= 2 g
M
= 210 mm
J
and
M
of
the
angular
α
-
m
M
= 210 mm
J
and
M
and
J
calculate
the
- J diagram.
J
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