Write a formula describing the fuel usage of a car (in motion). [fuel usage = fuel used per second]
As an explanation, if I were describing how quickly my friend ate a meal from Mcdonalds I might postulate factors that affect how quickly he eats (slower when he's walking, he always eats some food regardless of all other factors etc...) and cobble those into a formula.
Present answer as a formula plus explanation of terms/assumptions
(You can of course ignore the formula bit if you don't fancy fiddling around in a non-Latex script)
PS. This is me posting a question I plan on throwing at my Physics tutees (As a mock up Oxbridge question). I want to know if the damn thing works
PPS. Using the riddles system to keep answers independent
HINTS
- Many cars have optimum efficiency at around 55mph (not that they burn less fuel/sec than at lower speeds but the reduced travel time balances out the extra fuel/sec) so a formula might want to qualitatively show that such a thing is reasonable
- Thinking about power (work rate of the car, how much work it does per second) and saying this is directly proportional to fuel used per second is a route into the question.
