Physics - April 2007

Suppose a star the size of our Sun, but of mass 8.0 times as great, was rotating at a speed of 1.0 revolution every 20 days. If it were to undergo gravitational collapse to a neutron star of radius 20 km, losing three quarters of its mass in the process, what would its rotation speed be? Assume that the star is a uniform sphere at all times and that the lost mass carries off no angular momentum.
in rev/day?

I asked this question previously, but did not understand the response given to it......it ended with finding the mass of the star when I obviously need the rotation speed.....anyways, could someone help?

2007-04-18 10:39:08 · 1 answers · asked by ping102_1999 1

2007-04-18 10:28:30 · 10 answers · asked by Anuradha S 1

Explain.

2007-04-18 09:53:11 · 6 answers · asked by Anonymous

2007-04-18 09:51:31 · 2 answers · asked by Anonymous

either the percent that do...or the percent that have the ability to.

2007-04-18 09:45:30 · 4 answers · asked by framling 1

If photons have zero mass, then their energy should be zero by E = m c^2 or E^2 = m^2 c^4 + p^2 c^2 because p = m v. If they have mass, they can't travel at the speed of light.

2007-04-18 09:41:29 · 4 answers · asked by Liquid Astatine 2

DC versus AC problem. Suppose your DC power supply is set to 15 V and the vertical setting on the oscilloscope is at 5 V/div. How many divisions will the trace deflect if you connect the output of the power supply to the scope with the "A input" switch set on DC? How many divisions if the switch is on AC?

2007-04-18 09:37:26 · 1 answers · asked by dietcoke 2

We know that hydrogen does exist in N = 3 dimesional space.
The assumption is that photons are massless,
therefore flux is equal to the charge inside closed surface.

2007-04-18 09:23:39 · 2 answers · asked by Alexander 6

Two rods of equal length L = 1.00 m form a symmetric cross. The horizontal rod has a charge of Q = 400.00 C, and the vertical rod a charge of -Q = -400.00 C. The charges on both rods are distributed uniformly along their length. Calculate the potential at the point P at a distance x = 3.00 m from one end of the horizontal rod.
Thank you !

2007-04-18 09:14:13 · 1 answers · asked by katiaisr 1

Why does the sound of thunder take so much longer to stop than the flash, which we see only a split second?

(note: I'm not asking why the thunder arrives later)

2007-04-18 07:46:01 · 15 answers · asked by Atrus 1

A large turntable rotates about a fixed vertical axis, making one revolution in a time of 6.40 s. The moment of inertia of the turntable about this axis is 1300 kg*m^2. A child with a mass of 44.0 kg, initially standing at the center of the turntable, runs out along a radius.

Part A) What is the angular speed of the turntable when the child is a distance of 1.90 m from the center? (Assume that you can treat the child as a particle.)

I have no clue how to solve this problem?

2007-04-18 07:24:15 · 1 answers · asked by ? 1

A rocket blasts off from a platform on a space station. An identical rocket blasts off from free space. Considering everything else to be equal, will the two rockets have the same acceleration? Explain.

2007-04-18 07:12:30 · 8 answers · asked by Wendy D 1

2007-04-18 06:46:10 · 6 answers · asked by Dex's Gal 3

scientists have come up with and named a force, but they can't explain it. my biology teacher told us about this. she says no one truly knows why atoms fall apart. i personally know how, but the majority of scientists will dismiss my knowledge because it has no proof. not every fact has proof after all, but i was just wondering if anyone on here knew how something that contains so much energy it should fly apart doesn't fly apart and stays together in the nucleus. no rude answers please. thanks

2007-04-18 06:28:31 · 5 answers · asked by Anonymous

What if the world was made up only of fermions, or only of bosons? I remember reading about this in a book a long time ago, but I don't remember much... :)

2007-04-18 06:22:55 · 3 answers · asked by Gergely 5

i have a DC motor that needs 230 volts from electricity to work if i reversed the rotation of the motor how many volts will the motor produce?

2007-04-18 05:26:09 · 6 answers · asked by Anonymous

2007-04-18 05:06:32 · 5 answers · asked by fatima a 1

Given the equation e=mc^2 what is the value of energy in my body?
Please describe in a comparable context.

In theory...does this value vary between fission and fusion nuclear reactions?

2007-04-18 04:42:35 · 3 answers · asked by LUCKY3 6

How high above the earth would you have to go before your weight would be one quarter (1/4) of its value on the earth's surface?

2007-04-18 04:18:54 · 4 answers · asked by Yarka 1

2007-04-18 03:57:53 · 6 answers · asked by Anonymous

2007-04-18 02:02:50 · 8 answers · asked by Mike R 1

i am working on a time machine my idea is to rotare an object at speed of light is time affected ? does gluons loosen and protons and neutrons tear apart

2007-04-18 01:40:39 · 14 answers · asked by ggkvarma 2

2007-04-18 00:47:07 · 8 answers · asked by Anonymous

2007-04-17 23:40:35 · 17 answers · asked by Anonymous

For example, there is that paradox that says, the distance between two points can be divided infinitely.

Common counters to this that I have seen are:
"as the distance decreases, so does the time it takes to travel the distance"
-so what? lol I don't understand what difference that makes, as time can also be infinitely divided!

"if you keep dividing infinitely, the sum of all the individual pieces will add up to the total distance"

-You say you divide infinitely, but if you divide infinitely then there will be an infinite number of pieces, and no matter what you do with infinity, you still end up with infinity. Infinity minus infinity is infinity. Infinity plus infinity is infinity. Infinity plus one is still infinity!

That answer is a paradox! It says that there are an infinite amount of divisions yet a finite amount of pieces.

Can anyone give a logical answer why the zeno paradox isn't really a paradox?

2007-04-17 23:26:53 · 5 answers · asked by worried person 1

The wingspan of a concorde aircraft is 25.6m. The aircraft cruises at an altitude of 35000 feet and travels at 550ms^ -1.

=> Explain whether the size of the e.m.t produces between its wing - tips depends on what direction the aircraft is flying at a particular place.

2007-04-17 22:31:05 · 1 answers · asked by adsion l 1

Two horses pull horizontally on ropes attached to a stump. The two forces vector F1 = 1340 N and vector F2 that they apply to the stump are such that the net (resultant) force vector R has a magnitude equal to that of vector F1 and makes an angle of 90 degrees with vector F1

Find the magnitude of vector F2 (in Newtons)

Find the direction of vector F2 (relative to vector F1).((in degrees))

2007-04-17 21:53:39 · 2 answers · asked by Anonymous

Calculate the moment of inertia of a bicycle wheel (with 8 spokes (thin rods) evenly spaced around the wheel) rotating around its center. Approximate the tire as a thin ring.

2007-04-17 21:34:44 · 3 answers · asked by playb0ybunny55 1

2007-04-17 19:54:06 · 1 answers · asked by Anonymous

The question, background and picture is all at the link below, it is multiple choice.

I am lost on how to do this problem, if someone could please show me how, I'd really appreciate it

http://img376.imageshack.us/img376/6687/34ac6.jpg

2007-04-17 19:43:59 · 1 answers · asked by Anonymous