Pete the 20 [kg] penguin slides down a rough slope passing through two checkpoints that are both equipped to read his total energy. At point 1 his total energy is 250 [J] and point 2 his total energy is 160 [J]. If point 1 is 0.8 [m] above point 2 and he has speeds of 3 [m/s] and 4 [m/s] through points 1 and 2 respectively, how much work is done by the non-conservative forces in this system?

Pete the 20 [kg] penguin slides down a rough slope passing through two checkpoints that are both equipped to read his total energy. At point 1 his total energy is 250 [J] and point 2 his total energy is 160 [J]. If point 1 is 0.8 [m] above point 2 and he has speeds of 3 [m/s] and 4 [m/s] through points 1 and 2 respectively, how much work is done by the non-conservative forces in this system?