I've been working on this question and I just don't know how to arrive at the correct answer!! Here's my question. Two identical cars, each travelling at 50km/h, one travelling north and one travelling east, collide at an intersection and become locked together. What is the speed of the joint wreck immediately after the collision? I tried using the pythagoras theorum to attempt finding the new speed. Root(50^2 + 50^2) but this gave me a new speed of 70.7km/h which I believe is wrong since the are moving at a faster speed. How do I solve this question?