A workshop wheel is spun and then allowed to slow down.
The kinetic store of the wheel decreases by 28 J. The thermal stores of the wheel and axle increase by 19 J, and the thermal store of the nearby air increases by 9 J.
The wheel, axle and nearby air are treated as a closed system.
A student concludes that the increase in the thermal stores means that energy has been lost from the system.
Explain why the student's conclusion is incorrect.