Hello, I am working on the following problem and cannot figure out if I am doing the problem incorrectly or if my professor gave us the wrong answer. (I think that the former is the issue.) 1. The problem statement, all variables and given/known data[/b] To a stationary observer two frogs at opposite ends of a 100m long lake jump into the water at exactly the same time. To an observer flying overhead along the length of the lake at a velocity of 0.6c, one frog enters the water sooner than the other. a) How much sooner? b) How long is the lake to the flying observer? 2. Relevant equations Δt' = (Δt - (v/c^2)Δx) / sqrt(1-(v^2/c^2) Δx' = (Δx - vΔt) / sqrt(1-(v^2/c^2) (And the inverse of these) L = Lo sqrt(1-(v^2/c^2)) 3. The attempt at a solution a) Using the Lorentz transformation equations, I got Δt' = 2.5^-7s. This is also what my solution set says. b) Using the length contraction formula, and saying that the proper length is 100m (because that is the rest length). I get 80m. I think this makes sense because the length is longest in the rest frame. However (and this is how the solutions say to do it), using the Lorentz transformation and plugging in the known Δx = 100m, and known Δt = 100m, you get 125m. The answer itself does not make sense to me, however working through the problem using the Lorentz transformation seems reasonable. I just don't understand why the two do not agree. And which one is correct? Any and all help would be much appreciated!