Physics Questions

[some1nu]

Hi,

 

I need help with the following questions, any help would be greatly appreciated

 

Find the flaw in the following "contradiction": According to relativity, length (or distance) decreases and time increases as speed increases. Since speed is the ratio of distance to time, however, speed should decrease as distance and time increases

 

In the Michelson-Morley experiment, no interference pattern was found. This meant that both light beams completed the same total distance in the same time. What would be a corresponding result in the boat-river analogy? what would be its signifigance?

[JaKiri]

Find the flaw in the following "contradiction": According to relativity, length (or distance) decreases and time increases as speed increases. Since speed is the ratio of distance to time, however, speed should decrease as distance and time increases

 

2x/2y = x/y = 1000x/1000y. Distance and time increase in exact proportions (1 over gamma), and this only applies for things not moving at the speed of light in any useful sense anyway.

 

SR has two axioms (although these are fairly easily proved):

 

1. The speed of light is invariant for all observers.

2. All rest frames are equally valid.

 

If I see something going away from me at 3/5 c, then they see me going away from them at 3/5 c. The only difference is when it's a recession speed between an object and a moving rest frame, in which case it's (a-b)/(1-ab/c^2), or the same with + instead of minus.

 

Try that equation with one of the speeds being the speed of light, c; you'll find out that c will always be approaching or receding at c, no matter the speed of the other object.

 

In the Michelson-Morley experiment, no interference pattern was found. This meant that both light beams completed the same total distance in the same time.

 

Because the speed of light is invariant for all observers.

 

What would be a corresponding result in the boat-river analogy? what would be its signifigance?

 

Given that the boat analogy (if you're thinking of the same one) is used to demonstrate how light is not like a boat on a river, travelling with a medium, its significance is that... light is not like a boat on a river.

[swansont]

Hi' date='

 

I need help with the following questions, any help would be greatly appreciated

 

Find the flaw in the following "contradiction": According to relativity, length (or distance) decreases and time increases as speed increases. Since speed is the ratio of distance to time, however, speed should decrease as distance and time increases

[/quote']

 

 

The time changes as measured by a different observer—they don't both change for the same observer. i.e. if Alice and Bob are moving relative to each other, Bob will see Alice's clock run slow, and Alice will see the distance along her motion contract. (and the situation is symmetrical) "The "contradiction" is that relativity has been incorrectly applied.

[some1nu]

Hi,

 

thanks for the quick replies. I am having trouble with one more question from the same unit, if somebody could help me out that would be great

 

Einstein's formula for the total energy of a massive object is mc^2=m0c^2+Ek, where m0c^2 is the rest energy and Ek is the kinetic energy. The formula seems to omit potential energy. Does it, however? Explain.

[swansont]

Hi' date='

 

thanks for the quick replies. I am having trouble with one more question from the same unit, if somebody could help me out that would be great

 

Einstein's formula for the total energy of a massive object is mc^2=m0c^2+Ek, where m0c^2 is the rest energy and Ek is the kinetic energy. The formula seems to omit potential energy. Does it, however? Explain.[/quote']

 

 

Consider this: look at the mass of, say, a proton, neutron and electron, and compare it to that of deuterium, which is the combination of the three.

[some1nu]

kind of lost would m0c^2 be the potential energy? does anyone anyone know how to explain the answer to this question? thanks

[swansont]

kind of lost would m0c^2 be the potential energy? does anyone anyone know how to explain the answer to this question? thanks

 

I'm trying to get you to explain it. Which has more potential energy, the particles by themselves, or the atom after it has formed?