Physics - December 2007

or forces act on the Moon and explain how Newton's third law of motion applies to the system.

2007-12-21 05:19:58 · 5 answers · asked by supercalofragilistic 3

I've heart that in some conditions, hot water will freeze faster then cold water, how is this possible?

2007-12-21 05:07:23 · 7 answers · asked by meatismurder90 3

The rod has lenght L=1, occupies segment from (-1/2,0,0) to (+1/2,0,0) and its mass GM = 1 pulls the gas by gravitation.
As a result pressure at point (1,0) is Po =1.
How many moles of gas is under pressure greater than Po?

The rest of the data are mostly ones too:
length of the rod is L = 1,
mass of the rod is GM = 1,
temperature of gas is RT = 1,
molar mass of the gas is μ=1/2.

2007-12-21 03:23:33 · 2 answers · asked by Anonymous

I don't understand SNR. When I read Wiki (ofcourse the best reference on earth ;) ) - It saids that it is the ratio of meaningful information to noise. I need to use SNR with imaging modalities. And this is confusing because many things happen during the imaging process. For example a CT or MRI scanner has very complicated techniques to reconstruct the picture from the basic signals. It may use filtering, averaging, back projection, interpolation -who knows what more... but the original signal- information is manipulated: So at what stage should you measure SNR if you want it to reflect the qualitity of your imaging modality?

Another strange thing is that the SNR seems to reflect more what I am measuring rather than the measuring apparatus itself. For example if I measure velocity with something- the faster the thing goes the more signal I may get: so a higher SNR. -but this says nothing about the measurement apparatus itself.

Please help me to understand SNR.

2007-12-21 02:28:44 · 4 answers · asked by ? 3

And there's nothing there(not hot solid/liquid iron), will I float? Cause of that's the center of gravity. The EXACT earth's center of gravity will make me float cause I'm pulled to every sides and angles.

2007-12-21 02:17:48 · 11 answers · asked by Anonymous

Hey, I'm just 14 okay! And what the 'E','=' and 'mc2' means? You know, those are abbrevations right?

2007-12-21 01:34:21 · 11 answers · asked by Anonymous

The gravitation has been explained to act as space time curvature. All different celestial objects create depression on a rubber sheet like universe.These pits have to be dynamic because 1. all the celestial objects are in motion and the pits created by them are also constantly changing. 2.All the galaxies are also moving away from each other so they are also constantly affecting the structure of the space time curvature. Then what is the rate of change of this curvature ? is it instanteous or it travels at the speed of light?. If it is instantneous then it must travel faster than light because the galactic distances are in light years. And if it travels at the speed of light then the gravitation has a finite speed.

2007-12-21 00:43:02 · 6 answers · asked by kishan j 1

2007-12-20 19:32:13 · 17 answers · asked by Anonymous

I'm doing a hobby project.. that is to generate AC electric inside a tire (or rotating rim).

A marble (magnet) will move inside the rotating tire (or rim), which its inner layer will be covered with coils.. there shall be a relative movements which can induce the voltage. As the tire/rim rotates, the marble will also rotating.

Problem is, i can't figure out how to make that marble move inside the rotating tire.

Or, does anyone else have any idea on how to induce voltage from a rotating tire (besides using the dynamo attached at the side of the tire). The voltage must be induced from INSIDE the tire)

2007-12-20 18:43:13 · 3 answers · asked by Anonymous

I need to build a projectile launcher for class.

I do not want to do it but am trying

I have to fling a golf ball, which is about 1.62 ounces or 45.93 g.

the catapult or trebuchet has to be under 50x50 cm

and it has to fling it a distance of at least 12 meters

anyone have any help?

I've been trying to use the internet but.. beh

2007-12-20 17:30:22 · 2 answers · asked by Rachelll 2

2007-12-20 17:13:44 · 1 answers · asked by exile_india 1

I hope I have spelt It correctly.

2007-12-20 16:51:41 · 1 answers · asked by Tony S 1

2007-12-20 16:09:34 · 12 answers · asked by anica_808 2

if you have seen Mission Impossible three, can you please tell me about the scene where tom cruise sticks the bad guy's head out of the plane? i need to know for a science project if the man could actually live after have so much air pressure on his face. thanx. (give detailed answers please)

2007-12-20 15:44:17 · 2 answers · asked by AmyBaby 2

I don't know if this makes sense, because I have no idea what the answer is.

2007-12-20 15:24:11 · 5 answers · asked by kperk_56 2

At what point can you no longer add more heat (can't get hotter than the heat source which would be the surface of the sun) but what happens the the rest of the energy that you are focusing into that point, dose it just disapate faster and how much increase in heat do you get out of each multipel focus of the beam of sunlight.
I'v tried to look this up and found different answers but can not get the whole thing but together if someone could explaine it in laymans terms I would really appreciate it
Thank you in advance if you can help.
John k

2007-12-20 14:24:34 · 3 answers · asked by John K 2

A 1.00×104kg railroad car is rolling at 6.00m/s when a 8000kg load of gravel is suddenly dropped in.

Kevin is standing on a sheet of ice that covers the football stadium parking lot in Buffalo, New York; there is negligible friction between his feet and the ice. A friend throws Kevin a ball of mass 0.400kg that is traveling horizontally at 10.0 m/s. Kevin's mass is 67.4 kg. If Kevin catches the ball, with what speed v(f) do Kevin and the ball move afterward? I got this right, which was 5.9 cm/s, but I don't understand how to get the second part: If the ball hits Kevin and bounces off his chest horizontally at 7.50 in the opposite direction, what is his speed v(f) after the collision?

2007-12-20 14:20:30 · 3 answers · asked by nothankyou1110 2

A m1 = 4.80 kg block on a smooth tabletop is attached by a string to a hanging block of mass m2 = 2.30 kg, as shown in Figure 6-29. The blocks are released from rest and allowed to move freely.

the figure is at this url.... http://www.webassign.net/walker/06-29alt.gif

Find the Acceleration of the blocks and the tension in the string
-->acceleration should be in m/s^2
-->tension should be in newtons


If you could solve this it would be much appreciated!! thanks

2007-12-20 14:12:59 · 7 answers · asked by xoxo-oth 2

Also, what is einstein's general theory of relativity and how does it account for the blackness of black holes?

2007-12-20 13:36:57 · 4 answers · asked by Anonymous

Pretend you have a rod, hung from an axis at one of its ends like this.

0-------------------------------

The rod rotates from this horizontal position.

Determine the angular velocity of the rod, as a function of (theta) (theta is the angle through which the rod has swung.)

Please show steps and add details, thank you.

2007-12-20 13:24:59 · 1 answers · asked by Anonymous

Using g = m/r^2?
What is the acceleration due to gravity at an altitude of 1.00 x 10^6 above the earth's surface, given that the radius of the earth is 6.38 x 10^6 m?
How do i go about solving that?

2007-12-20 13:07:38 · 2 answers · asked by Voldemort 2

a 100kg crate is resting on level ground, with a cluster of helium balloons tied to the top. The helium balloons provide an upward force of 100 N.
a) Draw a freebody diagram of the forces on the crate.
b) Calculate the force of gravity on the crate.
c) If you must apply a 1000 N force to get the crate to move, what is the coefficient of static friction newt(s)?
d) If you apply a horizontal 1100 N force to the box, what will be its rate of acceleration?(consider friction)

2007-12-20 12:51:17 · 5 answers · asked by Alonso 1

2007-12-20 12:47:00 · 5 answers · asked by P Srey 1

2007-12-20 12:42:32 · 1 answers · asked by nicole 15 1

2007-12-20 12:39:21 · 1 answers · asked by coolseantadlock 1

A 31 kg cannon ball is fired from a cannon with muzzle speed of 864 m/s at an angle of 32.9 degrees with the horizontal.
Gravity is 9.8 m/s/s.
A.) Use conservation of mechanical energy to find the maximum height reached by the ball.

B.) A second identical ball is fired at an angle of 132 degrees.
What is teh total mechanical energy at the maximum height of the second ball. Answer in units of J.

Please show your work and thanks for the help!
Happy Holidays!!!!!

2007-12-20 12:34:49 · 1 answers · asked by Anonymous

hi. i really need help with a couple of problems. i can't seem to figure these out at all.

okay, here's the first one:

Two charges, -14 and +4.4 µC, are fixed in place on the x axis at x = 3.0 m and x = 0 m, respectively.

(a) At what spot along the x axis is the net electric field zero?

(b) What would be the force on a charge of +15 µC placed at this spot?


the other question is:

A tiny ball (mass = 0.014 kg) carries a charge of -22 µC. What electric field (magnitude and direction) is needed to cause the ball to float above the ground?





If you could help me with either of those problems or both, it would be really helpful. thanks.

2007-12-20 12:28:35 · 1 answers · asked by chicagolakers 2

DOG question, could you be of any help?

2007-12-20 12:27:46 · 3 answers · asked by Anonymous

A mini black hole traveling near light speed hits the earth and pass right through. Because of its speed, the only matter it eats is matter directly in front of its path. Assuming it converts 50% of the matter it consumes directly into energy. And it has a frontal area of 10 cm^2. How big of a blast will it create just going through the atmosphere before it hits the earth?

[I recently messed up on a similar question ;-)]

2007-12-20 12:02:42 · 4 answers · asked by Frst Grade Rocks! Ω 7

please help me get it right!!!


Question 1: An m2 = 1.4 kg can of soup is thrown upward with a velocity of v2 = 5.2 m/s. It is immediately struck from the side by an m1= 0.5 kg rock traveling at v1= 8.2 m/s. The rock ricochets off at an angle of α = 65 degrees with a velocity of v3= 5.4 m/s. What is the angle of the can’s motion after the collision? Answer in units of degrees.

Question 2: With what speed does the can move immediately after the collision? Answer in units of m/s.

2007-12-20 12:00:04 · 1 answers · asked by Anonymous