Can anyone help with this hw?

Question

I am having trouble with these types of physics problems. There are several like the one below that are on my homework. I have the answers but don't know how to get the answers. 

If a spaceship is 30m long and has a mass of 25,000kg. You travel at .95 c for 1 year. 
a) How much time has passed on earth? 3.2 years
b) How long does the spaceship look to an oberver at rest? 9m
c)What would the mass of your spaceship be realtive toa an observer at rest? 8000kg

I know that for A you use the equation ∆T=∆to/√1-v^2/c^2. For B, ∆L=∆to/√1-v^2/c^2. For C, ∆M=Mto/√1-v^2/c^2. What I don't know though is what to plug into the equations and how to get the answers. Can anyone explain this to me?

Steve · Accepted Answer

Lorentz factor γ = 1/√[1 - (v/c)²] = 3.2

a)  T = T'*γ = 3.2 yr
b)  L = L'/γ = 9.4 m
c)  M = M'*γ = 80,000 kg

You dropped a zero on (c).....

oldschool · Answer

The Lorentz Factor y = 1/sqrt[1-(v/c)^2] = 1/sqrt[1-0.95^2] = 1/0.31225 = 3.2

a) T = To*y = 3.2yr
b) L = Lo/y = 30/3.2 = 9.4m
c) M = Mo*y = 25,000*3.2 = 80,064kg

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Can anyone help with this hw?

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