<span>You’ve asked for two, but there are three factors according to Newton’s theory of gravity. They are:<span>the mass of the object,the mass of the source of the gravitational field andthe distance between the object and the source.</span>An object’s gravitational potential energy is directly proportional to the negative of the product of the first two factors mentioned above (the masses), and inversely proportional to the third (the distance). </span>
When the two waves collide, because they are both crests there is constructive interference. This mean that at the point of collision the amplitude increases.