Aspring stores potential energy u0 when it is compressed a distance x0 from its uncompressed length. a] in terms of u0, how much energy does it store when it is compressed twice as much? uel/u0 =? b] in terms of u0, how much energy does it store when it is compressed half as much? uel/u0 = ? c] in terms of x0, how much must it be compressed from its uncompressed length to store twice as much energy? x/x0 = ? d] in terms of x0, how much must it be compressed from its uncompressed length to store half as much energy? x/x0 = ?