Physics - September 2006

2006-09-17 12:32:21 · 7 answers · asked by Storm 2

I am applying Gauss' Law to an elementary situation: A sphere of radius r containing a uniform charge density rho, with an electric field normal to the surface of constant value E. Gauss' Law has two forms, integral and differential. See http://en.wikipedia.org/wiki/Gauss%27_law In the integral form, the surface integral of E (normal component) equals the total charge enclosed divided by e0. Since E is constant, the surface integral result is just E times the surface area 4*pi*r^2*E. The total charge enclosed is rho times the spherical volume, or (4/3)*pi*r^3*rho; therefore 4*pi*r^2*E = (4/3)*pi*r^3*rho/e0. The result is E=(1/3)*r*rho/e0.

The other form is div(D)=rho, or div(E)=rho/e0. In spherical coordinates div(E)=(1/r^2)d/dr(r^2*E). For E=constant, this is (1/r^2)*(E*2*r), or 2*E/r. So using the differential form I get
E=(1/2)*r*rho/e0.

One method gives a 1/3 multiplier, the other a 1/2 multiplier. What am I doing wrong? Which one is right?

2006-09-17 12:18:37 · 1 answers · asked by gp4rts 7

2006-09-17 12:18:07 · 16 answers · asked by Eduardo V 1

If time travel is possible, then how come we have never met anyone who has? or have we, and they are just keeping it a secret?Its proberly that nerdy kid no one really likes at school...

2006-09-17 11:34:10 · 28 answers · asked by Advertise here! 2

Terminal velocity: 75 m/s
Air resistance: 750 N
Force due to gravity: 750 N
Air resistance increases by 100 N with every 10 m/s increase in velocity.

2006-09-17 10:47:52 · 6 answers · asked by Runnie 1

2006-09-17 10:26:08 · 16 answers · asked by reyno 1

Ok, here it is: An electron is moving in a circular path around a long, uniformly charged wire carrying 2.5 nC/m. What is the electron's speed? Answer: 2.8 Mm/s. Please help me with the process.

2006-09-17 09:45:04 · 3 answers · asked by thomthum2000 2

would a helicopter in an elevator (hovering in mid air) move in relation to the elevator? or would it stay in its original position while the elevator moves around it?. I suppose this could happen in a moving truck as well. if the helicopter is hovering and the truck is moving forward, will the helo hit the back wall of the truck?

2006-09-17 09:20:29 · 10 answers · asked by Rhumor 1

2006-09-17 09:14:37 · 5 answers · asked by foxy lady 2

Basically, I want to include the overlapping sections in the physics equation for friction Fn=mu*N, however most sites simply reference the existance of the coeffient, or state that it can not be calculated.

I understand that the surfaces of the materials are different, but there must be a relationship between the sizes that is proportional enough to envelope in an equation.

2006-09-17 09:01:19 · 5 answers · asked by Merranvo 2

2006-09-17 08:55:43 · 3 answers · asked by Eric Inri 6

Ice was available on luxury ocean crossings, and ice boxes throughout the summer months, usually delivered by the "Ice Man". How was it made, and how was it stored before refridgeration?

2006-09-17 08:43:09 · 6 answers · asked by Canadazeus 1

2006-09-17 08:15:27 · 4 answers · asked by nookala 2

If a bullet was fired while the guns barrel is touching the face, and then fired, would you hear the gunfire before you die? Or would the bullet travel faster than sound into your head and kill you?

2006-09-17 08:09:25 · 12 answers · asked by XillegalxactionX 1

So how much energy is required to lift a 1 lb object in the air?
And how does this relate to a 10 lb, 100 lb, and 1000 lb object?

Like if you were trying to make a flying car... i know sounds weird

2006-09-17 08:05:59 · 6 answers · asked by Anonymous

2006-09-17 07:57:42 · 56 answers · asked by arun bose 1

....why do they twinkle, and not when you look at them close up?

2006-09-17 07:50:36 · 11 answers · asked by quite contrary 1

2006-09-17 07:36:20 · 5 answers · asked by arun bose 1

2006-09-17 07:32:32 · 8 answers · asked by arun bose 1

2006-09-17 07:20:33 · 9 answers · asked by john b 1

2006-09-17 07:00:22 · 7 answers · asked by Sir Nickle Barsteward 3

A plane or jet pulls or pushes air to maneuver. Space has no air, so just what is it that allows a space craft to turn?

2006-09-17 06:41:13 · 7 answers · asked by sng18whlr 2

2006-09-17 06:07:01 · 15 answers · asked by Anonymous

V=(8 V/m^4) (x^2) (y^2) + (3.9 V/m^4) (z^2) (x^2 - 6 m^2) + (6.6 V/m^4) (y^3) (z)

considering (x, y, z):

What is the y component of the electric field at (1.7m, -4m, 6.6m)? Answer in units of V/m.

Any help would be greatly appreciated, keep in mind that the above equation is equal to the potential, not the E field

2006-09-17 05:29:49 · 2 answers · asked by to the beat in my head 3

2006-09-17 05:28:35 · 4 answers · asked by wilmer jr p 1

a. When a Follow through is needed when a golfer hits the ball with the golf club, what law applies to this situation?

b. When a cigarette vendor has to move with the bus as he jumps off the bus, what law applies to this?

c. When a car still moves for a short period after the brakes are applied, what law could have been applied to this?

Pls. help I need to pass this tomorrow!

2006-09-17 05:19:21 · 3 answers · asked by Aerich 1

In 1919 during a solar eclipse, Arthur Eddington observed the light from stars passing close to the sun was slightly bent, so that stars appeared slightly out of position, apparently confirming Einsteins theory and leading to the curved universe theory. Was Arthur not simply observing the bending of light rays due to the heat of the sun, the same effect that causes mirage's?

2006-09-17 05:04:41 · 2 answers · asked by Gruesome Gary 1

How does the earths gravitation affect it, is it going to remain stationary, or will the earth move under it? Why?

2006-09-17 05:04:34 · 5 answers · asked by Benji 1

Albert Einstein said,
"Everyone who is seriously interested in the pursuit of science becomes convinced that a spirit is manifest in the laws of the universe--a spirit vastly superior to man, and one in the face of which our modest powers must feel humble."

2006-09-17 04:58:35 · 5 answers · asked by curious_inquisitor 1

a)How much later does it reach the bottom of the cliff?
b)What is its speed just before hitting?
c)To what height will the stone rise from the edge of the cliff?
d)what total distance did it travel?

2006-09-17 04:49:03 · 2 answers · asked by Kelly 1