Compress a spring with 10 pounds. Measure amount it has compressed. Now it does not mater what you use, one scale and a weight, your hand, or another scale to compress spring to the second scale, 10 pounds is 10 pounds and spring will compress same amount. In the case with two scales both scales will show ten pounds not 5 or 20.
But now, if I try to push a spring against the wall, the spring will absorb some of this force by compressing, no? So... if I want to push against the wall with ten pounds of pressure, I may have to use 15 pounds of force, as it may take five pounds of pressure to first compress the spring. Energy must come from somewhere, and go somewhere. The spring absorbs and stores energy.
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