Multi choice Q15 (2 Viewers)

[Pwnage101]

lets calculate: (btw this is q5)

using the relativity formula, its clear 0.63 s pass between consecutive tiks of the clok as seen from earth

however, lets assume it has to travel that extra distance the ship has traveled in the 0.5s, distance = speed x time = 1.8e8 x 0.5 = 9e7

thus extra distance teh wave must travel is 9e7

time = distance/speed, assuming radio waves travel at c time - 9e7/c = 0.3s

thus it takes an extra 0.3 s, thus the difference will be 0.63 + 0.3 = 0.93s

which is NOT one of the options, however the answer of d is achieved if ive made a mistake and it ends up being 0.15 instead of 0.3s for extra time - where have i gone wrong??

 

[mynamewastaken]

this is my idea of q5 (off topic). its pobably wrong, but i got a because, the time on the ship is Tv, so the time on earth is To, so shouldnt it be smaller than Tv? so i picked a), as it was the only smaller value... but im not sure if i got confused between Tv and To..

 

[Kearnzo]

lets calculate: (btw this is q5)

using the relativity formula, its clear 0.63 s pass between consecutive tiks of the clok as seen from earth

however, lets assume it has to travel that extra distance the ship has traveled in the 0.5s, distance = speed x time = 1.8e8 x 0.5 = 9e7

thus extra distance teh wave must travel is 9e7

time = distance/speed, assuming radio waves travel at c time - 9e7/c = 0.3s

thus it takes an extra 0.3 s, thus the difference will be 0.63 + 0.3 = 0.93s

which is NOT one of the options, however the answer of d is achieved if ive made a mistake and it ends up being 0.15 instead of 0.3s for extra time - where have i gone wrong??

My knowledge is pretty hazy on this but

I think the Doppler effect is incorporated into the Lorentz equations.

Lorentz equations were orginally made to compare frames of reference that were travelling at different speeds I think? The Doppler effect was part of this.

Then Einstein sorta found the physical reason behind the equation. I guess :S.

Bit tricky. I thought of that aswell but realised yeh it wouldnt work out. Wouldve tricked the people who thought too much if they put 0.93

 

[lionking1191]

If you used the time dialation formula for 5 you got (c), but since the ship is moving away at a constant speed it's gunna take extra time for the signal to get to earth - so the answer had to be (d)

lol EM waves travels with constant velocity c regardless of motion of origin. looks like you outsmarted yourself there :uhhuh:

 

[adosh]

for question 27,,,,wiht the ohms law. who thinks we had to subtract 2 form the resistance answer???????????/

 

[vy137163]

But because the speed was so large, the distance it travels in one such is significant enough to make it (d) I think

Your just confusing people...

 

[Aaron.Judd]

for question 27,,,,wiht the ohms law. who thinks we had to subtract 2 form the resistance answer???????????/

Possible, not really sure. It would help if someone could scan that page of the paper and upload it.

 

[poisonives]

Ua answer is pretty accurate i have only one question though where is the acceptor band relative to the conduction and valence band?

[tnks i meant semiconductor.]

the acceptor level is just above the valence band, and further below the conduction band

 

[JamesTockuss]

lol EM waves travels with constant velocity c regardless of motion of origin. looks like you outsmarted yourself there :uhhuh:

Ahhh you dont get it. Ok so time dialation would cause the stationary observer on earth to receive a signal every 0.63 seconds - but this is only if the distance between the source and the receiver is not moving. Since the source is moving AWAY then the time between pulses will be 0.63 + extra.

Like I said earlier, it's kind of like the red shift of stars that are moving away from us. Because they are moving away the observed 'frequency' of the light (and in this case the time between pulses) increases.

You didn't need to work it out with maths or anything - it was more logic. It had to be greater than 0.5 (time dialation), and it had to be greater than 0.63 - leaving the only answer as D.

 

[undalay]

Ahhh you dont get it. Ok so time dialation would cause the stationary observer on earth to receive a signal every 0.63 seconds - but this is only if the distance between the source and the receiver is not moving. Since the source is moving AWAY then the time between pulses will be 0.63 + extra.

Like I said earlier, it's kind of like the red shift of stars that are moving away from us. Because they are moving away the observed 'frequency' of the light (and in this case the time between pulses) increases.

You didn't need to work it out with maths or anything - it was more logic. It had to be greater than 0.5 (time dialation), and it had to be greater than 0.63 - leaving the only answer as D.

Yes. It is known as the relativistic doppler effect. However, taking into account this doppler effect the time interval should be exactly 1 second. However (D) was only 0.78 seconds, so I assume BOS did not want us to take this into account.