A cyclist notices that the chain of her bicycle is dry and rusty.
Explain why the bicycle is less efficient when the chain is dry.
In one minute, the cyclist does 12 000 J12\,000\ \text{J}12000 J of work on the pedals.
2400 J of this energy is transferred to the thermal stores of the chain, the gears and the surroundings.
All the remaining energy is transferred usefully to move the bicycle.
Calculate the efficiency of the bicycle.
The cyclist oils the chain. The efficiency of the bicycle increases to 0.90.
Calculate the energy that is now wasted when the cyclist does 12 000 J12\,000\ \text{J}12000 J of work on the pedals.