How can I calculate the drag force of a car on a hill?

AI Thread Summary
To calculate the drag force (FD) of a car on a hill, a force balance can be applied since the car is moving at a constant speed of 55 mph on a 3.18-degree incline. Given the car's mass, rolling resistance, and other parameters, the resultant force is zero, allowing for the calculation of FD without needing the drag coefficient (CD) initially. The formula for CD can then be used once FD is determined. The discussion emphasizes the importance of understanding the relationship between speed, resistance, and forces acting on the vehicle. Ultimately, applying these principles will enable the calculation of both FD and CD effectively.
philo2005
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Hi

I am currently trying to work out the drag coefficient of a car, I know the formulae to work out CD, this being CD=FD/0.5xρv^2A. I can not figure out how to find FD as the formulae for this requires CD. Is there another way to find FD? The information I have is as follows:

Car Mass: 1350 kg
Rolling Resistance: 400 N
Cross Sectional Area: 2.2 m^2
Density of Air: 1.23 kg m^-3
Hill Gradient: 3.18 degrees

To find CD the equation below is used

CD=FD/0.5xρv^2A

However to find FD CD is requiredAN ATTEMPT AT THE SOLUTION WOULD BE

?FD?/0.5 x 1.23 kg/m^3 x 24.590 m/s^2 x 2.2

It is just the FD part I am not too sure about.I would greatly apprecitate any help offered as I am now completely stumped.

Thanks
 
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Are you given the acceleration of the car?

If you are you can apply a force balance on the car to get the value for FD.
 
Hi yes I am given a speed of 55mph.
 
Are you given time or distance or anything to work out the acceleration or work done by the car?
 
Hi

Sorry you asked for acceleration in your previous post and I gave you speed :redface:

I am not given acceleration but I am told that it is on a hill that is 3.18 degrees to the horizontal.

EDIT: Sorry I already mentioned that. It maintains a constant speed of 55mph.
 
philo2005 said:
Hi

Sorry you asked for acceleration in your previous post and I gave you speed :redface:

I am not given acceleration but I am told that it is on a hill that is 3.18 degrees to the horizontal.

EDIT: Sorry I already mentioned that. It maintains a constant speed of 55mph.

Then you should apply a force balance on the car, since it is moving at constant speed then the resultant force on the body is zero.

If you do that then you can get FD and hence CD
 

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