Relativity help ASAP! (1 Viewer)

[ixsamanthaxi]

1) Alpha Crucis is 522 light years away from us. Imagine that a spacecraft was able to travel to that star at a speed of 0.9999 c.

a) How long does the trip take, as observed from earth?

b) How much time has passed on the craft's clockes, as seen from earth?

c) How much time has passed on Earths clocks, as seen from the spacecraft?


2) A pole vaulter runs with his 5-metre pole through a shed that s only 4 metres long. The pole vaulter is capable of reaching a speed of 70% of the speed of light over a short distance. Suppose that the shed also has a back door.

a) Show that it is possible for a stationary observer to see the entire pole disappear into the shed (however briefly)

b) Explain why the runner will not perceive a time when his pole is entirely within the shed, and suggest how the two observations can be reconciled.
(hint: it has to do with the Principle of Simultaneity)

thanks anyone in advance! i am going insane with these two questions!!!

 

[cybob101]

a)522* 1/0.9999
b) 7.382748513years
c)522* 1/0.9999

CBF

 

[Dumbledore]

2a) cbf but mostly likely due to the length contraction formula, the pole will fit in the shed as observed by the stationary observer

b) as the pole is stationary in the runners refernce frame, the length of the pole will remain 5m and he/she will not see the pole entirely in the shed at the same time, this is explained by the law of simultaneity

law of simultaneity states that oberservations in one reference frame are not necessarily the same in another

EDIT: u might note that the shed is moving at 0.7c relative to the runner, so he/she will observe a length contraction in the shed 2, but this isn't required in the explanation

 

[cybob101]

lol this is my favorite part of space easy formulas= win

 

[anom1ly]

1) Alpha Crucis is 522 light years away from us. Imagine that a spacecraft was able to travel to that star at a speed of 0.9999 c.

a) How long does the trip take, as observed from earth?

b) How much time has passed on the craft's clockes, as seen from earth?

c) How much time has passed on Earths clocks, as seen from the spacecraft?


2) A pole vaulter runs with his 5-metre pole through a shed that s only 4 metres long. The pole vaulter is capable of reaching a speed of 70% of the speed of light over a short distance. Suppose that the shed also has a back door.

a) Show that it is possible for a stationary observer to see the entire pole disappear into the shed (however briefly)

b) Explain why the runner will not perceive a time when his pole is entirely within the shed, and suggest how the two observations can be reconciled.
(hint: it has to do with the Principle of Simultaneity)

thanks anyone in advance! i am going insane with these two questions!!!

1
a) 522/0.9999 = (ans) in light years
b) (ans)x (1-0.9999^2)^1/2 = (ans2) in light years
c) i could be wrong on this. it should be the same as (b). its like the twins paradox scenario. you can't take preference of one reference frame over the other.

2
a) u'd use length contraction equation to show that 5m can be reduced to 4m when v = 0.7
b) the runner will see the world around him get shorter, but not himself. this is because relative to him, the world is moving at 0.7c