Joe is standing next to his garage. He has placed a sign pointing the way to his

Question

Joe is standing next to his garage. He has placed a sign pointing the way to his house 2 km up the road from the garage. Sally is racing toward him in her new, jet-propelled sports car at a speed of v=0.5c.

a) What is the rest length of Joe's garage if, according to Joe, Sally's car can just fit inside the
garage? Assume the rest length of Sally's car is 4m.
b) As Sally passes the sign, she turns on her headlights to signal Joe that she is coming.
How long does the light take to reach the garage (i) according to Sally, and (ii) according to
Joe?

Explanation / Answer

a)l=4/root(1-0.25c^2/c^2) l= 4.61880215 b)i)according to sally it will be 2/(c-0.5c)=4/c=1.33*10^-8 s ii)according to joe velocity=c t=2/c=6.66*10^-9 s

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