Download - Physics labs with flavor
1 Copyright 2010 M. AGREST
Physics labs with flavor
Physics and Astronomy Department
College of Charleston,Charleston, SC
Charleston, SCOctober 23, 2010.
Southern Atlantic Coast Section American Association of Physics Teachers
Workshop for Physics and Physical Science Teachers
2 Copyright 2010 M. AGREST
Recurrent learning in Physics Labs
Abstract: The principle of recurrent studies as a way to bring flavor into Introductory Physics labs was discussed earlier 1,2. Participants will get some hands-on experience of Recurrent Studies and feel excitement due to the flavor it brings into the introductory Physics Labs You will perform forward study of a phenomenon and calculate unknown parameters based on your own measurements and assumptions. After discussion you will set up the backward study. The purpose of it is to evaluate how accurate was your result in the direct study. Here the parameter of interest in forward study stays unchanged, but others will change. Based on your measurements of some of them and the result of the forward study, you have to predict one (or more) parameters.Then you will perform the backward experiment to measure the value of the predicted parameter and calculate the percent error for your prediction. We expect that you will experience excitement (as students have) and you will be motivated to try the recurrent studies method for innovation of your teaching.1. M.M. Agrest, “Physics labs with flavor,” Phys. Teach. 47, 297 (May2009)2. M.M. Agrest, “Physics labs with flavor II,” Phys. Teach. (in print for 2011)
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
3 Copyright 2010 M. AGREST
1. Forward study Students study the phenomenon, perform the experiments, analyze the data and make conclusions about the results. find a quantity as a feature of the phenomenon
/Based on theoretical model, the measurement results, statistics, etc/2. Backward study
New assignment; Based on the results in 1. find the quantity of a questioned parameter.
3. Shoot for your grade Perform the new experiment in the presence of the instructor Compare the results with the prediction Get your Grade
Shoot for your grade General Idea
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
4 Copyright 2010 M. AGREST
Momentum & Energy 1
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M+m
Kinematics
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
5 Copyright 2010 M. AGREST
Momentum & Energy 2
V0 M
m
M+m
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(mVm 0)b VmM (m M)12
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Kinematics
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
6 Copyright 2010 M. AGREST
x-x0
hH
Bernoulli
Fluid Mechanics
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
7 Copyright 2010 M. AGREST
Bernoulli2
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Fluid Mechanics
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
8 Copyright 2010 M. AGREST
Reflection and Refraction
1.00i airn n
Snell’s Law
sin sini i t tn n
sin
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n n
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sin sin
t i
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prism
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it 2i
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Determine Index of Refraction
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
9 Copyright 2010 M. AGREST
Total Internal reflection
1 2
1 2 1 2
2 2
12
1 1
1 2 180
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1sin 2
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SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
10 Copyright 2010 M. AGREST
Focal Length of a Converging Lens
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f
1
si
1
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1
2
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Backward study Assignment:
Based on your result for the focal length f for a given So predict Si
Forward study
Optics
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
11 Copyright 2010 M. AGREST
Focal Length of a diverging Lens
1
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1
si1
1
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1
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# so sif fave
1
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…..
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Backward study Assignment:
Based on your result for the focal length f predict Si for a given So
AForward study
Optics
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
12 Copyright 2010 M. AGREST
INTERFERENCE
y
L
Laser
m b sin;
sin yL
b y
mL
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sin ;
sin
sin
m d
y
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Waves of Light
y
L
Laser
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
13 Copyright 2010 M. AGREST
3R
4R
5R
Fig. 1a
V4
1R
2R
V
Fig. 1b
V9
R7R6
R10
V
R8
R9
The forward study. Finding voltage of the power source. Terminals of one of the resistors (let us say resistor R4) in the circuit are accessible, so students can measure the difference of potentials (V4) across
this resistor. Based on the measurement of the voltage, students have to calculate the voltage V of the power source. The experiment is repeated several times as follows: Replacing this resistor by a different resistor, students calculate the voltage of the power source several times and estimate the error of their results.
Backward study. Finding voltage across the test resistor. The test circuit (Fig.1b) consists of the same power source providing the same value of the voltage as in the forward study to a different circuit. The assignment is: calculate the voltage drop across one of the resistors based on the experimental value of the voltage supplied. The test circuit can be completely different or it can be the same one with the replaced testing resistor.
Experimental assessment. Comparing the results. After the “predicted” voltage is announced, the measurement should be performed and the answer is announced. Usually this event attracts students from all other groups of the lab as it is accompanied with shouts “Hurrah”, “Yes!” and other expression of satisfaction. The grade for this part of the lab should be based on the percent error in the predicted value of voltage.
Resistors in a circuit
Electricity
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
14 Copyright 2010 M. AGREST
3R
4R
5R
Fig. 1a
V4
1R
2R
V
Fig. 1b
V9
R7R6
R10
V
R8
R9
Resistors in a circuit
• Construct a circuit according the diagram 1.Here: R1=2 k R2=6.5 k R3=5.5 kR4=1.5 kR5=4.5 k•Using a voltmeter, measure V4, • based on the measured V4 calculate V of the power source.
• Construct a circuit according the diagram 2.Here: R6=4 k R7=3.5 k R8=2.5 kR9=5.5 kR10=1.5 k•Using the calculated value of V from part 1, calculate V9. measure V4, • based on the measured V4 calculate V of the power source.
Electricity
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
15 Copyright 2010 M. AGREST
Resistors in a circuit
Construct a circuit according the diagram 1.Here: R1=2 k R2=6.5 k R3=5.5 kR4=1.5 kR5=4.5 kInstructor will set the variable power source at Voltage V unknown to you.Using a voltmeter measure V4, based on the measured V4 determine V of the power source.When the same resistors arranged with this power source into another circuit, find voltage drop V4 across its resistor R4
diagram 2
1R
2R
3R
4R
5R
V
diagram 1
4VR2
R4
R1
R5
V
R3
4V
Electricity
SACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
16 Copyright 2010 M. AGREST
Speed of Sound in the AirAssignment 1Given: Tuning fork with a given frequency f.
Find: Speed of Sound in the air. vsound T
f
L1 1
4
L2 3
4
L3 5
4
fv fsoundf 3213
1
Assignment 2: Result from the Assignment 1:
Find frequency of “unknown” (test) tuning fork.Measure: at resonance to find as in (1);Then find
iL
soundv
f Assignment 2Alternative: Use result from the Assignment 1: Set where you expect the resonance based on given frequency f of the test tuning fork.Compare the with one which lets you get the loudest Woo…ooo…ooo
vsound T
f
iLiL
4
5L
WavesSACS AAPT Physics Labs with Flavor Mikhail M. AgrestFall 2010 Recurrent studies.
17 Copyright 2010 M. AGREST
The END
Visual assessment of students’ prediction of the results emotionally involves them and makes the learning process more effective, brings popularity into the discipline because it involves hands-on experience, using and testing the students’ results during their lab work.