# Physics

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Jemima is sanding some floorboards with an electric sander which has a power rating of 360W. Jemima has the sander on for 45 minutes. The Sander is only 55% efficient. The electricity supplier charges 14.8p per kWh. What will be the cost of the 'wasted' energy?
I know how to work out the total cost but not the wasted energy cost...

• Physics -

Eff. = Po/Pi = 0.55
360/Pi = 0.55
Pi = 360/0.55 = 654.55 Watts = Power in

Energy Wasted = 0.65455kW * (45/60)h =
0.491 kWh.

Multiply Energy wasted by the cost per kWh.

I don't know what 14.8p mean.

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