# Foo - A lesson in physics

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View Full Version : A lesson in physics

timmyquest
07-26-06, 10:49 PM
A brief lesson in centrifugal force, i'll leave it to phun physics.com to explain it in words, and youtube.com to show you with "pictures"

An object traveling in a circle behaves as if it is experiencing an outward force. This force, known as the centrifugal force, depends on the mass of the object, the speed of rotation, and the distance from the center. The more massive the object, the greater the force; the greater the speed of the object, the greater the force; and the greater the distance from the center, the greater the force.

It is important to note that the centrifugal force does not actually exist. We feel it, because we are in a non-inertial coordinate system. Nevertheless, it appears quite real to the object being rotated. This is because the object believes that it is in a non-accelerating situation, when in fact it is not. For instance, a child on a merry-go-round is not experiencing any real force outward, but he/she must exert a force to keep from flying off the merry-go-round. Because the centrifugal force appears so real, it is often very useful to use as if it were real. The more massive the object, the greater the force. We know that this is true because an adult will have a harder time staying on a merry-go-round than a child will. The greater the speed of rotation, the greater the outward force. We know that this is true because a merry-go-round is harder to stay on, the faster it rotates. If you move further out on the merry-go-round, you will have to exert a greater force to stay on. In order to stay on a circular path, we must exert a force towards the center called centripetal (or "center-seeking") force. Consider a rope with a ball on the end. You can swirl the ball around in a circle over your head while holding onto the rope. The ball experiences the so-called centrifugal force, and it is the rope that provides the force to keep in moving in the circle.

Stupid kids of America
Bored kids of America
Clever kids of America

Mothra
07-27-06, 02:12 AM
Centripedal...

KingTermite
07-27-06, 06:52 AM
And here is another lesson in Physics.....a flash tutorial to understand the 10 known dimensions using string theory.
http://www.tenthdimension.com/flash2.php (click on "Imagining the Ten Dimensions" on left nav bar).

eubi
07-27-06, 07:18 AM
Arrrrg! I was just ready to get to work when you posted this!

Acceleration is defined as the rate of change of velocity. Most often, we feel acceleration when we drive our car away from a stop light. It pushes us back into the seat. We are speeding up, the velocity is changing, and we experience acceleration.

When a ball is swung in a circle on a string, we have acceleration even though the angular velocity of the system is constant. This is because the direction of the velocity vector is changing. We have a rate of change of velocity, so we have to experience acceleration.

By the way, the rate of change of acceleration is "jerk". :D

Class dismissed.

Stacey
07-27-06, 07:50 AM
mein Gehirn ist in den Schmerz!

eubi
07-27-06, 01:30 PM
Gee Stacey, it made perfect sense to me.

But right now I have to finish my Klein bottle full(?) of water and get back to work.

"Arbeit Macht Frei"

Crono
07-27-06, 02:06 PM

As you approach the speed of light, a photon will still escape from you at the speed of light.

It's one of the basic ideas in relativity, and I still get mindfuct thinking about it.

KingTermite
07-27-06, 02:41 PM

As you approach the speed of light, a photon will still escape from you at the speed of light.

It's one of the basic ideas in relativity, and I still get mindfuct thinking about it.

Are you trying to make a joke from the old hypothetical question:

If you were in a Volkeswagon bug traveling at the speed of light, what happens when you turn the headlights on?

edp773
07-27-06, 02:45 PM

Other weak areas:

I never knew a centrifugal clutch could believe what situation it is in!

It must be a phsycological thing when a person passes out at six or seven Gs.

Crono
07-27-06, 03:34 PM
Are you trying to make a joke from the old hypothetical question:

If you were in a Volkeswagon bug traveling at the speed of light, what happens when you turn the headlights on?

It's not so hypothetical. Funny thing is, when I first heard that I immediately retorted with that answer. They were like "It's sort of a buddhist koan, you're supposed to ponder the answer or something"

C'mon now, Einstein predicted it over half a century ago. Moving clocks appear to tick more slowly relative to their stationary counterparts. But this effect only becomes really significant at very high velocities that approach the speed of light. Personal (relative) time is slowed down, and thus the photon can escape from you at the constant of light speed.

Fascinating, no?

tcar5
07-27-06, 03:41 PM
much more simplistic lesson for us cyclist types: If your feet leave the pedals and the midline of your back extends too far left or right of the saddle, then your ass is going to hit the ground. I have proven this time and time again......