The amplitude of superposition of two waves y1 = 5sinwt and y2 = 5coswt is

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.

54 degrees incident angle = reflected angle

angle is from normal turned to line of ray