Absolute fallacy.yep, but surely she coasts down the other side, therefore only driving 50% of the way.
Ride a bike on the flat.
Ride a bike up and down hills.
Do you get back the energy expended going up when you go down?
Not at all.
Hilly country is harder work than flat country.
With an internal combustion engine, the engine turns over and powers the wheels. The car weighs 1000kg maybe and takes a great deal of energy and fuel to get it up. Coming down, gravity pulls the car of course so very little fuel is used. Trouble is, this doesn't cancel each other out. Pity really.
Drive your car on the flat for ten miles constant speed. Note the fuel consumption.
Drive your car uphill for a mile, downhill for a mile and do this five times same speed total distance ten miles. Note the fuel consumption.
Tell me now that the two consumption figures are the same.
Try it.
Mick.