ATAR Notes: Forum

HSC Stuff => HSC Science Stuff => HSC Subjects + Help => HSC Physics => Topic started by: 006896 on July 01, 2021, 09:07:07 pm

Title: Relativistic velocity question help
Post by: 006896 on July 01, 2021, 09:07:07 pm

Hi!
Could someone please help with how to answer this question? I'm thoroughly confused. I'm sure we need to apply the Lorentz factor to the time and distance and then use v=s/t, but I'm sure how to do this.
Thank you!

Title: Re: Relativistic velocity question help
Post by: fun_jirachi on July 02, 2021, 02:50:18 pm

If you're stuck, this is a good read. For small velocities we would assume it is 0.7c + 0.7c = 1.4c; but we know this is impossible as nothing can exceed the speed of light. However, as we approach the speed of light we have to take into account relative time dilation and length contraction, which makes velocity addition for small velocities obsolete.

Title: Re: Relativistic velocity question help
Post by: 006896 on July 02, 2021, 06:00:49 pm

Quote from: fun_jirachi on July 02, 2021, 02:50:18 pm

If you're stuck, this is a good read. For small velocities we would assume it is 0.7c + 0.7c = 1.4c; but we know this is impossible as nothing can exceed the speed of light. However, as we approach the speed of light we have to take into account relative time dilation and length contraction, which makes velocity addition for small velocities obsolete.

Thanks! Is there a way to do this question without using that formula? Surely we should be able to apply a Lorentz transformation maybe twice somewhere, to get the answer?
I'm not too sure how to do it myself, but any solutions would be helpful!