Physics - December 2007

Einstein arrived at some of his ideas by picturing himself riding on a beam of light. What if that beam were slower due to passing through a medium? Would that affect simultaneity across the boundary of the medium? Wouldn't distant stars be seen in the more distant past? We know that time runs slower on the outside of a rotating disk than it does on the inside. Does time run at a slightly different rate underwater? This has no effect on relativity - in fact, I am trying to live within the confines of relativity.

2007-12-03 02:55:46 · 2 answers · asked by Larry454 7

How are acting two forces which are affectring on masses weighting 3 and 5kg, if the both masses have the same velocity?

2007-12-03 02:32:35 · 1 answers · asked by Scary Girl 6

If every person in the boat is going to apply the same amount of force when they row no matter what the others in the boat are doing, why does it matter if they're all rowing together? I understand that all rowing together results in a stronger individual burst, but why is one strong burst any stronger than multiple weak bursts when the sum is the same?

I understand theoretically that if everyone's moving at once, the resistance to individual rowers appears lower - but why is that, if they're still applying the same amount of force?

2007-12-03 02:19:22 · 10 answers · asked by Anonymous 3

and play the child why

2007-12-03 00:39:45 · 2 answers · asked by sundeep 9732 1

wikipedia states:

"The origin of the use of p for momentum is unclear. It has been suggested that, since m had already been used for "mass", the p may be derived from the Latin petere ("to go") or from "progress" (a term used by Leibniz)."

could you give more info besides the ones stated above?

thank you very much:))

2007-12-03 00:01:24 · 4 answers · asked by Grand Phuba 5

The membrane that surrounds a certain type of living cell has a surface area of 5.0 x 10^ -9 m^2 and a thickness of 1.0 x 10^ -8 m. Assume that the membrane behaves like a parallel plate capacitor and has a dielectric constant of 5.0. (a) If the potential on the outer surface of the membrane is +60.0 mV greater than that on the inside surface, how much charge resides on the outer surface? (b) If the charge in part (a) is due to K+ ions (charge +e), how many such ions are present on the outer surface?

2007-12-02 23:42:14 · 1 answers · asked by sunday 1

A parallel plate capacitor has a capacitance of 7.0x 10^-6 F when filled with a dielectric. The area of each plate is 1.5 m^2 and the separation between the plates is 1.0 x 10^ -5 m. What is the dielectric constant of the dielectric?

2007-12-02 23:40:24 · 1 answers · asked by sunday 1

What voltage is required to store 7.2 x 10^ -5 C of charges on the plates of a 6.0x10^ -6 F capacitor?

2007-12-02 23:33:40 · 1 answers · asked by sunday 1

how did they know that the speed of electromagnetic wave is 300 000 000 meters per second?

2007-12-02 22:44:09 · 7 answers · asked by Anonymous

This is our physics assignment so anybody could help me? thanks!

2007-12-02 22:32:26 · 7 answers · asked by James trighit 1

Why are some materials (iron, steel, heamatite) magnetic and others (like copper or aluminium) not? If it's about electron spin and alignment, why aren't all electrical conductors also magnetic or attracted to magnets even if they're not actually magnetic themselves, afterall they generate EM fields when a current is induced in them? Are there any magnetic or magnetisable non-metals? Why are only ferrous (iron based?) metals affected?

2007-12-02 21:59:57 · 1 answers · asked by Doom 2

1 An astrounaught on the Moon threw an object 4m vertically upwards and caught it again 4.5 seconds later. Calculate:
a) the acceleration due to gravith of the Moon,
b) the spped of projection of the object,
c) how high the object would have risen on the Earth, for the same speed of projection

2 A swimmer swims 100m from 1 end of a swimming pool to the other end at a constant speed of 1.2m/s, them swims back at constant speed, returning to the starting point 210 s after starting.
Calculate how long the swimmer takes to swim from: (i) the starting end to the other end, (ii) back to the start from the other end.

Please show working out and which equation of motion used!

2007-12-02 21:57:58 · 3 answers · asked by Selly 3

A 3900 kg truck traveling with a velocity of 11.5 m/s due north collides head-on with a 1450 kg car traveling with a velocity of 24 m/s due south. The two vehicles stick together after the collision.

What are the size and direction of the total momentum of the two vehicles after they collide?

2007-12-02 19:29:20 · 2 answers · asked by jay 1

A puck of mass 86.7 g and radius 3.73 cm slides along an air table at a speed of v = 1.53 m/s, It makes a glancing collision with a second puck of radius 5.12 cm and mass 120 g (initially at rest) such that their rims just touch. The pucks stick together and spin after the collision (b). The angular momentum of the system relative to the center of mass is 6.82e-03 kg*m^2/s.

I know that you have to use w=L/I i know you find the inertia for both pucks and i sort of know but i'm missing somethign the center mass is confusing me.

i found the center mass by doing(r1+r2)*m1/(m1+m2) but how do i put that in Inertia formula

any help is appreciated thanks in advance

2007-12-02 19:09:57 · 1 answers · asked by c c 2

A 75kg bobsled is pushed along a horizontal surface by two athletes. After the bobsled is pushes a distance of 4.5m starting from rest, its speed is 6.0m/s. Find the magnitudes of the net force on the bobsled.

2007-12-02 19:04:25 · 3 answers · asked by Belinda A. 1

Hi, working through a homework problem but I can't seem to get the answer to this one:

A steel gas tank of volume 0.0700 meters cubed is filled to the top with gasoline at 20 degrees celsius. The tank is placed inside a chamber with an interior temperature of 50 degrees celsius. The coefficient of linear expansion of steel is 12.0*10^-6 and the coefficient of volume expansion for gasoline is 9.50*10^-4 After the tank and its contents reach thermal equilibrium with the interior of the chamber, how much gasoline has spilled?

Any explanation of how to do this problem would be greatly appreciated!

2007-12-02 18:38:28 · 4 answers · asked by doubtful 2

Wikipedia has some excellent info, but doesn't cover some details I need, such as this one. Could I get a layman's answer, since physics principles are a bit over my head?

2007-12-02 18:25:05 · 2 answers · asked by Eric 3

If the center of the target is level with the rifle, how high (in cm) above the target must the rifle barrel be pointed so that the bullet hits dead center?
physics problem.
I try many times with no luck, need help!!!!!

2007-12-02 18:06:37 · 2 answers · asked by ocire7 1

A flywheel turns through 30 rev as it slows from an angular speed of 3.2 rad/s to a stop.
(a) Assuming a constant angular acceleration, find the time for it to come to rest.
in s
(b) What is its angular acceleration?
in rad/s2
(c) How much time is required for it to complete the first 15 of the 30 revolutions?
in s

2007-12-02 16:35:51 · 1 answers · asked by srl1143 1

I've tried reading about it on wikipedia and what not but simply can't understand the physics behind it all. Can someone answer(as much in layman's terms as possible) how scientists respond to this statement.

At some time early in the world, something was created from nothing.

2007-12-02 16:33:19 · 10 answers · asked by Anonymous

1. A baseball is hit at 30m/s at an agle of 53 degrees. Immediately, the centerfielder runs at a speed of 4m/s directyl towards home plate and catches the ball. How far was the outfielder from the batter when the ball was hit?
2. A famous motorcyclist plans to jump across a canyon that is .03km wide. To do this, the cyclist plans to jump off of a 30 degree ramp at a speed of 19.6m/s. Will he reach the other side?
WORK PLEASE

2007-12-02 16:32:45 · 1 answers · asked by Anonymous

In outer space two space modules are joined together by a massless cable. These probes are rotating about their center of mass, which is at the center of the wire, because the modules are identical (see the figure). In each probe, the cable is connected to a motor, so that the modules can pull each other together. The initial tangential speed of each module is v0 = 17.9 m/s. Then they pull together until the distance between them is reduced by a factor of 6. Determine the final tangential speed, which is vf for each module.

2007-12-02 15:54:30 · 1 answers · asked by Xiaolin L 2

I have answers so I would really like help with the actual work to figure it out! Thanks!

A small crack occurs at the base of a 15.0 m high dam. The effective crack area through which water leaves is 1.30 x 10^-3 m^2. Ignoring viscous losses, what is the speed of water flowing through the crack? (Chapter 10)
a. 14.0 m/s

2007-12-02 15:41:24 · 1 answers · asked by PinkyTrauma 2

I need help working these problems out... BUT I have answers so showing me the work would be great!

Many hot water heating systems have a reservoir tank connected directly to the pipeline, so as to allow for expansion when the water becomes hot. The heating system of a house has 76 m of copper wire whose inside radius is 9.5 x 10^-3 m. When the water and pipe are heated from 24 to 78 degrees C, what must be the minimum volume of the reservoir tank to hold the overflow of water? (Chapter 13)

2007-12-02 15:33:17 · 1 answers · asked by PinkyTrauma 2

TRUE OR FALSE:
1. The maximum height for any projectile occurs at 2/3 of the total time.
2. The time it takes for an object that is dropped from a train window to fall to the ground is dependent upon the speed of the train.

2007-12-02 15:30:09 · 1 answers · asked by Khadedra C 1

1. A nickel rolls at a constant velocity across a tabletop 1.05m high. It rolls off the side of the table and hits the floor 0.0375m away. How fast was the nickel rolling initially? Please include work

2007-12-02 15:24:16 · 1 answers · asked by Khadedra C 1

I was wondering if anyone had any info and links on the physics behind the theremin.

2007-12-02 15:04:59 · 2 answers · asked by Rich W 2

True or False

2007-12-02 15:00:41 · 3 answers · asked by Anonymous

2. A baseball (m = 140 g) traveling horizontally at 30 m/s moves a fielder's glove backward 35 cm when the ball is caught.

b. How much working was done on the ball?

c. What was the average force exerted by the glove on the ball?

2007-12-02 14:52:09 · 1 answers · asked by Robert 2

I heard that there is a "trick" or a phrase that you can use to memorize the electromagnetic spectrum.. Anyone know what it is?

2007-12-02 14:32:32 · 5 answers · asked by retrieverbark 2