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

[philo2005]

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

 

[rock.freak667]

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.

 

[philo2005]

Hi yes I am given a speed of 55mph.

 

[rock.freak667]

Are you given time or distance or anything to work out the acceleration or work done by the car?

 

[philo2005]

Hi

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

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.

 

[rock.freak667]

Hi

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

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 F_D and hence C_D