I've been working on this particular question for some time and am sure that it's very simple but I continue to get the wrong answer... An 18.0 N weight slides down a rough inclined plane which makes and angle of 29.0 degrees with the horizontal. The weight starts from rest and gains a speed of 15.0 m/s after sliding 150 m. How much work is done against friction? I am under the impression that 1) I need to find Wtotal by saying it equals 1/2mv^2 (note: because the weight is 18.0 N I devided it by gravity=9.81m/s to get kg) (I've done it both ways though) 2) Find Wgravity by saying it equals mgh 3) Use Wtotal = Wgravity + Wfriction rearranged to say Wfriction = Wtotal - Wgravity 4) vwala - the wrong answer (I know this has to be something easy, I'm just not getting it. Friction and I are not friends...) Choices are: a. 1100 J b. 1500 J c. -1500 J d. 229 J How should I be going about this?