A force of 10 lb is required to hold a spring stretched 2 in. beyond its natural length. How much work Wis done in stretching it from its natural length to 8 in. beyond its natural length? w=:m A cable that weighs 6 lb/ft is used to lift 650 lb of coal up a mine shaft 450 ft deep. Find the work done. Show how to approximate the required work by a Riemann sum. (Let x be the distance in feet below the top of the shaft. Enter x;* as xi.) lim E Ax n -+ 00 Express the work as an integral and evaluate. dx = ft - lb