Analysis: (1) According to the meaning of the question, the overlapping part of a triangle and a square is an isosceles right-angled triangle, and the right-angled side is 2x, from which the functional relationship between y and x can be obtained;

(2) Substitute the value of X into the functional relationship of (1) to get the value of Y;

(3) Substitute half the area of the square into the functional relationship of (1), and the value of x can be obtained. (In fact, AB and DC coincide at this time, which means that the distance that the isosceles triangle moves is just the side length of the square, so x=5. Solution: (1) Because the overlapping part of triangle and square is an isosceles right triangle.

So y = 2x2.

(2) In y=2x2,

When x=2, y = 8；;

When x=3.5, y = 24.5.

(3) in y=2x2

Because when y=50 and 2x2=50,

So x2=25 and x=5 seconds (negative values are discarded).