The maximum speed of a child on a swing is 4.9 m/s. The child’s height above the ground at the lowest point is 0.7 m. How high above the ground is he at his highest point? http://img208.imageshack.us/img208/9949/untitledyx0.png [Broken] Above is the work done to solve the problem. I don't understand how they went from the blue to the red equation. Wouldn't the two g's cancel out since you would need to divide the left side by mg?