A physicist grabs the ends of a DNA strand with optical tweezers and stretches it 28 . How much energy is stored in the stretched molecule if its spring constant is 0.046 ?
(1/2) k x^2
(1/2) (.046) (28)^2
but 28 what ???? surely not miles. k what??? Carats per toe length??
Better get this all in sci units if you want Joules.