A railroad track and a road cross at right angles. An observer stands on the road 70 meters south of the crossing and watches an eastbound train traveling at 60 meters per second. At how many meters per second is the train moving away from the observer 4 seconds after it passes through the intersection?

Question

oobleck · Accepted Answer

The distance z is z^2 = 70^2 + (60t)^2 at t=4, z=250 z dz/dt = 120t Now plug in your numbers