Formula for area of trapezoid is (b1+b2) divided by 2 then multiplied by height. So b1 + b2 is 9 + 12 which is 21. Then divide 21 by 2 you get 10.5. then multiply that by height, 10.5 x 6. The area is 63 feet squared.
For this case we have the following equation: Where, w: The weight of a spring in pounds E: the energy stored by the spring in joules. Substituting values we have: Making the corresponding calculation: Answer: the approximate weight of the spring in pounds is: