PHY 185, EXPERIENCING
THE PHYSICAL WORLD, X - 3
NEWTON'S LAWS: ACCELERATION, ACTION-REACTION & FIELDS
Today's hands-on experiences focus upon Newton's 2nd and
3rd laws. Motion with and without friction are investigated
via a short (amusing) film, the Departmental hovercraft, rockets and rolling
desk chairs. The relative intrinsic "strength" of gravitational, electric,
magnetic and nuclear forces is a secondary topic of interest. Physics is
Fun!
1. Video I: "A Million to One"
Another classic from our film vault, this short clip highlights motion
without friction. It's also a real hoot and the sound track is
nothing short of inspirational!
2. Video II: - "Weighing the earth: Measurement of G" (not g)
This video shows us how Henry Cavendish "weighed the earth" by measuring
the universal gravitational constant (G = 6.67 x 10-11 N m2/kg2).
Cavendish (of Cavendish Laboratory fame) performed this experiment in 1798
and essentially quantified the intrinsic strength of the gravitational
force. We normally think of that force as being quite large. However, this
is due to everyday interaction with a very large mass (Mearth
= 5.98 x 1024 kg!). Gravity is by far the weakest of the four
fundamental forces exhibited by nature.
3. RIDE A ROCKET!
Motion without friction and Newton's second and third law's is highlighted
using the Physics Department's hovercraft and a CO2 fire extinguisher.
Climb on and go for it, but don't hog the CO2.
4. ROCKETS PART DEUX: THE SEQUEL
A toy rocket is available for your edification. You can't ride this
one, but it is a bit more dramatic than part un. After you add water, take
it outside - try to keep it off the roof and away from trees and power
lines.
5. DESK CHAIR PHYSICS
Newton #2 and #3 again. Does it matter who pushes? Sit in the desk
chairs and push each other around. Students with different inertias illustrate
these laws best.
6. THE OTHER THREE FORCES - THEY'RE STRONGER THAN G!
Various electric, magnetic and (strong and weak) nuclear force demonstration
apparati are available for you to investigate. See if you can discover
the hierarchy of the strengths of the four forces for yourself.
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