1. The problem statement, all variables and given/known data A roller coaster is lifted up 50m above the ground to the top of the first hill and then glides down around the track at the bottom. If it had a velocity of 3.0 m/s at the top of the lift and loses 10% of its total energy to friction as it glides down, what is the roller coaster's final speed at the bottom. Sorry, I can't remember the mass (in the question, i didn't actually forget it). Thanks for any help!! 2. Relevant equations v2^2 = v1^2 + 2g (y1-y2) <- not sure if this is correct.. 3. The attempt at a solution v2^2 = 3^2 + 2(9.8)(50-0) v2^2 = 9 + 980 v2^2 = 989 V2 = 31.4 m/s I'm not sure how to apply the friction acting against without a mass... 9.8 - (9.8 x .1) 8.82 <- Maybe use this as acceleration instead..