1. Question. A 15 kg child slides from rest, down a playground slide that is 4.0m long. The slide makes a 40degree angle with the horizontal. The child's speed at the bottom is 3.2 m/s. What was the force that the slide was exerting on the child? Answer: 75 N [up the slide] 2. My Attempt. Ek = W = Efinal - Einitial *Einitial cancels out because the child was at rest right? So its 0m/s = 1/2(15kg)(3.2m/s)squared = 76.8 J Then I did: W = Ff(costheta)(deltad) Ff= W/(costheta)(deltad) = 76.8 J/(cos180)(4) = -19.2 N 3. Confusion: I'm confused as to what I or like what my next step is? Could you explain what I might've done wrong or what I have to do after this and why? Maybe explain me the concept behind it?