1.

If the work required to stretch a spring 3 ft beyond its natural length is 12 ft-lb, how much work (in ft-lb} is needed to stretch it 9 in. beyond its natural length\":I A 10 ft chain weighs 65 lb and hangs from a ceiling. Find theI work done (in ft-Ib) in lifting the lower end of theI Chain to the ceiling so that it's level with the upper end. Find the average value fare of the function Fen the given interval. .'x] = J}, [0, 25] A force of 10 lb is required to hold a spring stretched 4 in. beyond its natural length. How much work W is done in stretching it from its natural length to 7 in. beyond its natural length? W = ft-lb