PASCO ME-9837 Manuale utente
Instruction Manual
Manual No. 012-08862
Discover Centripetal
Force Kit
Model No. ME-9837
Model No. ME-9837
2®
Table of Contents
Equipment List........................................................... 3
Introduction ............................................................. 4
Equipment Setup ........................................................ 5
The Classic Centripetal Force Lab ..................................... 6
Velocity versus Force ................................................... 8
Velocity versus Mass ................................................... 9
Velocity versus Radius .................................................10
Questions ...............................................................11
Demonstrations .........................................................11
Appendix A: Technical Support .......................................12
Appendix B: Copyright and Warranty Information .................. 12
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Model No. ME-9837 Discover Centripetal Force Kit
3
Discover Centripetal Force Kit
Model No. ME-9837
Equipment List
Included Equipment Replacement
Model Number
1. Rubber stoppers
(sizes: 6, 8, 10, 11.5, and 13)
2. Hollow tube (2)
3. Plastic ties (10)
4. Yellow string (73 m) ME-9876
Additional Equipment Recommended
Safety goggles
Marking pen
Force Sensor CI-6746 or PS-2104
Hooked Mass Set SE-8759
Newton Spring Scale (20N) SE-8718
1 (#6)
1 (#8)
1 (#10)
1 (#11.5)
1 (#13)
2
3
4
* Please contact PASCO Technical Support when no replacement part number is provided.
Discover Centripetal Force Kit Model No. ME-9837
4®
Introduction
The Discover Centripetal Force Kit contains the materials necessary to
perform the classical centripetal force lab similar to the first example
listed in the table below. In addition, the Discover Centripetal Force
Kit can be used in conjunction with Force Sensors or Newton Spring
Scales.
Centripetal Force is an often misunderstood physical concept. Among
other things, the popular, yet, misused word "centrifugal" contributes
to students' misconceptions. An object moving in uniform circular
motion experiences a net inward-pointing force, called the centripetal
force. It is important for students to identify the agent for each force
that contributes to the centripetal force (net force) for an object moving
in uniform circular motion.
The table below gives examples of the centripetal force for certain
occurrences:
Included with the Discover Centripetal Force Kit are rubber stoppers
of widely varying masses. Convenient blue ties are provided to attach
the stoppers easily to the bright, sturdy string. In addition, (2) two
tubes are included to use for multiple lab groups. The tubes are
chamfered to decrease friction on the string.
Situation Centripetal Force
An object twirled in a horizontal
circle. Tension from the string.
Car driving in a circle. Static friction on the tires directed
toward the center.
A satellite. Force due to gravity.
A “centrifuge.” The normal force from the wall of the
“centrifuge.”
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Model No. ME-9837 Discover Centripetal Force Kit
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Equipment Setup
1. Cut a piece of string approximately 1 meter long and feed it through
the hollow tube.
2. Secure a plastic tie through the center hole in each stopper.
3. Tie one end of the string to the plastic tie to the stopper that is to be
used in the specific experiment.
4. Tie a loop at the other end of the string and hook a mass through the
loop.
Important! Please follow these SAFETY guidelines:
•Put on safety goggles!
•Make sure that no one is standing close to avoid hitting others!
•Hold the tube far enough away to avoid hitting self.
5. Firmly hold the tube and start rotating (spinning) the rubber stopper
as shown in the following photo (starting rotation). Continue
spinning the stopper until it reaches full rotation.
hollow tube
stopper
hooked mass
string (1m)
loop in string
plastic tie
Discover Centripetal Force Kit Model No. ME-9837
6®
Labs with the Discover
Centripetal Force Kit
The Classical Centripetal Force Lab
Set up the lab as shown in the general setup section.
Overview
In this lab, the dependent variable is always the linear velocity (v). The
independent variables are the radius (r), the hanging weight -
determined by the hanging mass (mh) - and the spinning mass (ms).
When the velocity is plotted as a function of one of the independent
variables, the other two independent variables must be kept constant.
It is important, therefore, to keep track of these values using the
following data table for each of the 3 sections of this lab:
Spinning mass:
starting rotation Spinning mass:
full rotation
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Model No. ME-9837 Discover Centripetal Force Kit
7
For each data point collected, students must:
• Select and mark a predetermined radius.
• Select and attach predetermined hanging and swinging masses.
• Adjust the "swing speed" until the predetermined radius is attained.
• Time ten (10) full rotations.
Calculate the Linear Velocity
To determine the linear velocity of the spinning mass, measure the
period (T) and the radius (r). To find the period, divide the time of the
10 full rotations by 10. To calculate the linear velocity (v) use the
following equation:
In order to maintain a constant radius, mark the string with a pen.
Practice spinning the mass and observing the mark on the string.
Calculate the Force
The centripetal force on the spinning mass is roughly equal to the
weight of the hanging mass. Measure the hanging mass and use this
value to calculate the centripetal force.
radius (m) mh(kg) ms(kg) V (m/s)
ν2πr
T
---------=
Discover Centripetal Force Kit Model No. ME-9837
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Velocity versus Force
While using the same spinning mass and maintaining the same radius,
students find the corresponding velocities for different hanging
masses. A graph of Force versus Velocity should yield a square root
graph and a relationship of
where k1is a constant.
Sample Data:
The following data is for a spinning mass of 22 g (#6 stopper) and a
radius of 0.5 m.
νk1F=
radius (m) mh(kg) ms(kg) V (m/s)
.5 .1 .022 4.4
.5 .2 .022 6.3
.5 .3 .022 8.0
.5 .4 .022 9.2
.5 .5 .022 10.2
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Model No. ME-9837 Discover Centripetal Force Kit
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Velocity versus Mass
While maintaining the same hanging mass and radius, students find the
corresponding velocity for different spinning masses. A graph of
Velocity versus Msshould yield a graph with the relationship of
where k2is a constant.
Sample Data:
The following data is for a hanging mass of 500 g and a radius of
0.5 m.
νk2
ms
------=
radius (m) mh(kg) ms(kg) V (m/s)
.5 .5 .022 10.0
.5 .5 .034 8.2
.5 .5 .056 6.4
.5 .5 .086 5.2
.5 .5 .109 4.5
Discover Centripetal Force Kit Model No. ME-9837
10 ®
Velocity versus Radius
While maintaining the same hanging mass and spinning mass, students
find the corresponding velocity for different radii. A graph of Velocity
versus Radius should yield a graph with a relationship of
where k3is a constant.
Sample Data:
The following data is for a hanging mass of 500 g and a spinning mass
of 56 g (#10 stopper).
νk3r=
radius (m) mh(kg) ms(kg) V (m/s)
.2 .5 .056 3.8
.3 .5 .056 4.9
.4 .5 .056 5.8
.5 .5 .056 6.5
.6 .5 .056 7.1
.8 .5 .056 8.2
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