1. The problem statement, all variables and given/known data An empty cart travels at 15 m/s as the rain begins to fall. The rain goes into the cart, and adds 10 kg of mass per second. 1) Will the rain cause the momentum of the cart to change? 2) Write an equation for the speed of the cart as a function of time. 3) How fast will this cart be moving after 200 seconds? 2. Relevant equations dp/dt = 0 delta p = 0 = m(dv/dt) + v(dm/dt) a = dv/dt 3. The attempt at a solution 1) No, a change in momentum in this system = 0 (as given by my teacher during the quiz). So mass will change due to rain, but velocity will adjust and there will be negative acceleration that will slow down the cart. Momentum, overall, will not change and will stay the same. 2) v(t) = 15 m/s - 0.15t m/s^2 0 = m(dv/dt) + v(dm/dt) -150 mkg/s^2 = 1,000 kg (dv/dt) -0.15 m/s^2 = dv/dt = a at = v 3) v(200) = 15 m/s - 0.15 m/s^2 (200s) = 15 m/s - 30 m/s = -15 m/s *If the cart is not on a slope or hill, it is probably already at rest by 200 s. IT has slowed considerably due to the rain. This was a quiz my teacher gave, and I only got the first question right. I now have a 33% grade (unfortunately, it's all or nothing => no partial credit...) :/ She also refuses to post a solution sheet or give us the answers, and insists that we find the solutions ourselves to enhance our understanding of the material... Can someone please guide me through what exactly I did wrong on this 3-part quiz? Thanks for any help!