Quote:
Originally Posted by Ladogaboy
So velocity might not be the right word to describe what I am talking about. So what force, specifically, is causing my car to require more energy to climb an incline than it does to maintain the same speed on level ground? For example, my car gets ~ 19 mpg cruising up a ~ 4% grade at 65 mph but gets ~ 28 mpg cruising at 65 mph on level ground. What's causing my car to burn that extra 30% energy?
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for hijacking the OP's thread and not answering his questions.
The specific force you are looking for, is the force of gravity that is causing you to burn the extra fuel. Why? because you are not only pushing the car through the air at 65 mph, same as on the flat lands, BUT IN ADDITION TO THAT, you are also lifting it vertically up the hill against the force of gravity that wants to pull you back down the hill.
Your vertical speed is not at the same speed as your horizontal rate, but you are moving up away from the center of the earth, and you are fighting gravity with a force equal to the entire weight of your vehicle. To climb a 5% incline at a constant speed requires twice as much power at 65 mph as just moving on flat land. How do you make more power--you burn more fuel. Hope this helps, i can supply the maths if you desire a numerical explanation.