3B Scientific Rotating System on Air Bed (230 V, 50__60 Hz) User Manual
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7. Sample Experiments
To make time measurements the following
instruments are recommended:
1 Mechanical stopwatch
U40801
or
1 Laser reflection sensor
U8533380
and
1 Digital counter (230 V, 50/60 Hz)
U8533341-230
or
1 Digital counter (115 V, 50/60 Hz)
U8533341-115
7.1 Uniformly accelerated rotation
7.1.1 Making a graph of rotation angle versus time
Recommended parameters:
Accelerating mass
m
M
= 2 g
Multiple pulley radius
r
M
= 10 mm
Additional weight
m
J
= 25 g, distance
r
J
= 170 mm
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-
ϕ diagram.
For the parameters recommended above, the times
are as follows:
10° 40° 90° 160°
250°
2 s
4 s
6 s
8
10 s
7.2 Angular acceleration as a function of torque
7.2.1 Angular acceleration with different accelerating
masses
Recommended parameters:
Angle of rotation
ϕ = 90°
Additional weight
m
J
= 50 g, distance
r
J
= 210 mm
Multiple pulley radius
r
M
= 10 mm
Accelerating masses
m
M
= 1 g, 2 g, 3 g, 4 g
•
Set up the experiment as described under 6.1.
•
Determine the times for the same angle of
rotation with different accelerator masses
m
M
and
calculate the corresponding angular accelerations
α.
•
Display the dependence of the angular
acceleration
α on the accelerator mass in an
m
M
-
α
diagram.
7.2.2 Angular acceleration with different multiple
pulley radius
Recommended parameters:
Angle of rotation
ϕ = 90°
Additional weight
m
J
= 50 g, distance
r
J
= 210 mm
Accelerating mass
m
M
= 2 g
Multiple pulley radii
r
M
= 5 mm, 10 mm, 15 mm
•
Set up the experiment as described under 6.1.
•
Determine the times for the same angle of
rotation with differing pulley radii
r
M
and
calculate the corresponding angular accelerations
α.
•
Display the dependence of the angular
acceleration
α on the radius of the multiple
pulley
r
M
in an
r
M
-
α diagram.
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
ϕ = 90°
Accelerating mass
m
M
= 2 g
Multiple pulley radius
r
M
= 10 mm
Distance
r
J
= 210 mm
Additional weights
m
J
= 0 g, 12.5 g, 25 g, 50 g
•
Set up the experiment as described under 6.1.
•
Determine the times for the same angle of
rotation with different additional masses
m
J
and
the same distance
r
J
, and calculate the
corresponding moments of inertia
J using
Equations 4, 5 and 1.
•
Display the dependence of the moment of inertia
J on the additional mass m
J
in an
m
J
-
J diagram.
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
ϕ = 90°
accelerator mass
m
M
= 2 g