You turn on the motor in problem 2 and it pulls the weight up 79 cm in 2.5 seconds. a. What is the total amount of mechanical energy expended by the motor in pulling up the weight

Suppose that 27 j of work is needed to stretch a spring from its natural length of 6 m to a length of 9 m. (a) how much work is needed to stretch the spring from 12 m to 14 m? j (b) how far beyond its natural length will a force of 78 n keep the spring stretched?