Given the two baselengths, and the perpendicular height of the trapezoid, you can actually find the perimeter through the pythangorean theorem because the perpendicular height or height that forms a right or 90 degree angle makes a right triangle(2 be exact because this is an isoceles trapezoid which has two adjacent right triangles).
After 1 sec it would be 65 m/s after 2 sec it would be 55 m/s after 3 sec it would be 40 m/s after 4 sec it would be 20 m/s and so on. The equation for this is S = 70 - (-5(t)) where s=speed and t=time passed
