Springs?? (10 lbs. at 22 ft/s)

[akash155]

How would we go about testing the amount of force needed to propel the ball 8 feet in the air and once we go about testing that, and based on that calculation how would we quantify that in order to find how much energy would have to go into the ball? For example, we did a lever arm experiment where a mentor jumped on a lever and the ball was on the other side. We have the numbers and have calculated the energy lost from the jumping onto the lever to the ball leaving the lever. But we don't understand where to go from that point and I also don't believe that we calculated correctly. Any help would be greatly appreciated. Also based on that number, how do we determine what strength of spring we need.