- #1
tomrule007
- 18
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Homework Statement
Ignoring air resistance is a large error when dealing with cars, especially when they are traveling at high speeds. Remember that air resistance depends on the speed squared F_ar=-Av^2.
A) draw a "FBD" for the car. show that the power required to keep a car going at a constant speed on a flat road against air resistance alone is proportional to the speed to the third power.
B)If your car consumes 20hp when traveling at a constant speed of 30mph. how much more power would it need to travel at a constant speed of 60mph under the same conditions?
Homework Equations
Not really sure what i should even start with for part A i used
Newtons second law and that's all i pretty much used so far
The Attempt at a Solution
A) For the free body diagram ill list the forces i included: Gravity(down), Normal force(up), Air resistance(left),Motor force=F(right)
so i can set F-F_ar=M*A (but it says the is traveling at a constant speed so i can just a=0 and then get
F=F_ar
So i think i did this part right but i don't know were to go from here to prove that the force is 3x the velocity
Any help would be appreciated -Thanks Tom