1. The problem statement, all variables and given/known data On a roller coaster ride the total mass of the cart - with passengers included - is 280 kg. Peak K is at 46.0 m above the ground, peak L is at 21.5 m. The speed of the cart at K is 17.1 m/s, at L it is 12.8 m/s. How much energy is lost due to friction between the two peaks? 2. Relevant equations Ke = 1/2mv^2 = mgh 3. The attempt at a solution I tried finding the Ke at the 2 different points and subtracting.. it didn't work . then i tried with the mgh and subtracted it, and it still didn't work. So i guess i'm confused on which of the given data i should use. Thanks alot!