Question

A weight hangs freely from the end of a spring. A boy then slowly pushes the weight upwards until the spring becomes slack. The gain in gravitational potential energy of the weight during this process is equal to :

• A. the work done by the boy against the force of gravity acting on the weight
• B. the loss of stored energy by the spring minus the work done by the tension in the spring
• C. the work done on the weight by the boy plus the stored energy lost by the spring
• D. the work done on the weight by the boy minus the work done by the tension in the spring plus the stored energy lost by the spring

Answer 1

The correct option is C the work done on the weight by the boy plus the stored energy lost by the spring

Work done by the boy on the weight$=$Work done against the gravitational force$-$Energy lost by the spring,

Hence boy has to work less in lifting the weight due to spring potential energy is being converted in gravitational potential energy of weight.