(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

The mass of a car is 1500 kg. The shape of the body is such that its aerodynamic drag coefficient is D = 0.380 and frontal area is 2.50 m2. Assuming that the drag force is proportional to v^2 and ignoring other sources of friction, calculate the power required to maintain a speed of 100 km/h as the car climbs a long hill sloping at 3.50° the answer is in horsepower

2. Relevant equations

R = .5DpAv^2

P = Fv

1hp = 746W

3. The attempt at a solution

Total force the engine needs to overcome is the gravitational force at an angle and air resistance.

To find force, F = mgsin(theta) + .5 DpAv^2. Plugs everything in, F = (1500)(9.8)sin(3.5) + .5(.38)(1.29)(2.5)(27.78^2) = 1370.3N

To find power, P = 1370.3(27.78) = 38067W, 38067W = 51 hp.

I don't think my answer is correct. Can anyone offer any insight as to why? Thank you in advance.

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# Homework Help: Power as a car going uphill

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