Plz help this is a quiz A stationary observer at rest sees a 2 kg block sliding to the right at a speed of 11 m/s toward a second block of mass 7 kg that is at rest. The two blocks collide elastically, with first block bouncing back and the second block moving to the right according to this stationary observer. Another person who is walking to the right at a speed of u sees the same collision but, interestingly, that person sees the blocks moving toward each other at different speeds and then (as a result of the collision) simply rebounding in the opposite directions at the same speeds at which they had approached each other. What is the speed, u, that this person must have been moving at with respect to the stationary observer? State your answer to the nearest 0.1 m/s.