1. A car accelerates 1800m down an incline of 1 in 4 at 0.4ms^2. The car has a mass of 4,000kg and the resistance to motion is 400N Determine: a) The Tractive effort required by using D'Alemberts principle b) The Tractive effort required by using the conservation of energy 2. Relevant equations a)F=ma, mgsin(theta) b) KE=1/2mv^2, PE=mgh 3. The attempt at a solution a) calculating intertial resistance f=ma 4,000 x 0.4 = 1600N calculating the angle of 1in 4 tan^-1(0.25) calculating gravitational force mgsin(theta) 4000 x 9.81 x sin(14.04)=9519.593816N I'm stuck after this, do I add my two values and my resistance to motion or subtract them? As for part b) I'm at a loss because I don't have any values for velocity to work out the change in KE nor do I have the height to work out PE. What am I missing here? Thanks everyone!