Q1.
We have seen that when a force is applied and an object is displaced, work is done on it. Does this cause the object to gain capacity to do further work?
Answer
Yes. Positive work done on an object gives it energy, and energy is the capacity to do work.
- A fielder does work on a cricket ball while throwing it. The moving ball then knocks the wicket over — it has done work on the wicket (Fig. 7.8a, b).
- Someone does work in raising a flowerpot to a window ledge. If the pot falls, it can damage what lies below — again it does work (Fig. 7.8c).
work done on the object = change in its energy (Eq. 7.3)
positive work → energy gained → capacity to do work on something else
positive work → energy gained → capacity to do work on something else
Why it happens: energy is not used up in the transfer — it moves on. The ball keeps the energy the fielder gave it until it meets the wicket, and then hands it over. When the ball does positive work on the wicket, the wicket does an equal negative work on the ball, so the ball loses exactly what the wicket gains.