Physics is Phun

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Physics is Phun

• David S. Wright
• Professor of Physics
• Tidewater Community College

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7 in 1 Survival Tool
Whistle Compass LED Light Magnifying
Glass Mirror Thermometer Empty Space
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Inverse Proportion Tool
Whistle Compass LED Light Magnifying
Glass Mirror Thermometer Empty Space
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Whistle
Intensity k/r2
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Whistle
fk/l
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LED Light
Ik/r2
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Magnifying Glass
Totally Inverse 1/f 1/do 1/di
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Thermometer
Liquid in Glass
Coiled Bimetal Strip
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Bimetal Thermometer
Radiusk/DT
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Mirror
Gives an Inverse of the Image
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Without Mirror
With Mirror
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Compass
Magnetic Field (B) of an ideal dipole, measured
along its axis?
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Bk/r3
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Empty Space

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Physics Olympics
Penny Barge
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Basket ball and Tennis ball
1 meter
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Simultaneous Equations
Conservation of Momentum
mBvB1mTvT1mBvB2mTvT2
Conservation of Energy
½ mBvB12 ½ mTvT12 ½ mBvB22 ½ mTvT22
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vB14.5 m/s vB1 0 m/s vT1 -4.5 m/s
vT1 -9.0 m/s
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This simplifes the equations
mTvT1mBvB2mTvT2
mTvT12 mBvB22 mTvT22
Now its great fun to solve these!!!
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mTvT1mBvB2mTvT2
becomes
vB2(mTvT1-mTvT2)/mB
Then
Then some factoring and hand waving occurs
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Eventually
mB.4 kg mT.07 kg vT2 6.3 m/s
Vfinal with respect to floor 10.8 m/s
Final Height5.8 m!!!!
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Bed of Nails
Ratios PF/A
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Pressure
Elephants Foot 6000 lb Elephant Foot 40
in2 PF/A6000 lb/40in2 150 psi
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Pressure
Womans Stiletto Heel 100 lb woman Spike
Heel 1/16 in2 PF/A100 lb/(1/16 in2)
1600 psi
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Bed of Nails
160 lb Professor/320 nails Thats only ½ lb
per nail!
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Inertia
Sylvester's law of inertia The number of
eigenvalues that are postive, negative or zero do
not change under a congruence transformation.
When a quadratic Q in n variables is reduced by
a nonsingular linear transformation to the form
Qy12y22yP2-yP12-yP22-yn2 the number P of
positive squares appearing in the reduction is an
invariant of the quadratic form Q and does not
depend on the method of reduction.
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Inertia
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Inertia
Average FreightTrain 55 mph 1 mile
Up to 3300 lbs
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Stay at Rest
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Stay in Motion
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Penny Barge
x
10 cm
x
10 cm
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Maximize Volume
V L W H L10-2x W10-2x
Hx V(x)x(10-2x)24x(x2-10x25) dV/dx04(x2-10x
25)4x(2x-10) dV/dx4(3x2-20x25)0
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Penny Barge
Solving by the Quadratic Formula x5
x5/3
5/3 cm
6 2/3 cm
6 2/3 cm
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Leaf Blower
The Leaf blower and toliet paper involves
Bernoullis Principle, Inertia, Force,
Acceleration, but most of all it proves that
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Physics is Phun