It takes 90 seconds to fill a cars petrol tank The petrol tank has a capacity of 45 L The pump has to lift the petrol 4m from the storage tank underneath the forecourt. 1 L of petrol weighs 6.8N How much work does the pump do in pumping the petrol?

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Hubert KaluznySecond year Imperial Computing student, with previous teaching experience.17.5k students helped

In order to fill the tank completely the pump would’ve had to lift 45 L of petrol by 4m. We can calculate this using the gravitational potential energy formula: E = mgh where m is the mass, g is acceleration due to gravity and h is the height difference. Since the question told us that 1 litre of petrol weighs 6.8N, the total weight of the petrol is 45 * 6.8 = 306N note that weight = mg so we now can plug this value into the formula: E = 306 * 4 = 1224 Joules