A man who was first standing runs from the point A.His speed is 40 m/s in B and 23 m/s in C,where the distance BC=30 meters..a) What work does the force of friction over the man ( m=60kg)? b) Find the max height reached by the man in the C level.. image here http://i.imgur.com/HVd7UH2.jpg I dont know how to find the quotient of the force of friction in the image? Because Work = -(quotient)* m*g*x.. I can find x because mv0^2/2+ +mv^2/2=mgh and I can find h,how about the quotient? does the angle help me? how about point b? please help me..