I have a question where an 80 kg skier goes down a 40 degree snow slope on wooden skis. The skier is 1.8m tall and .4m wide. I use the drag equation and get 53 m/s. However I am not sure how to add friction into this. Any guidance is appreciated. Oh, friction is .06. I am not looking for an answer only direction. The numbers were put down just in case. Thank you for your help.