The equation for potential energy is PE = mgh, where m = mass of the object (sled), g = acceleration due to gravity (9.8 m/s^2), and h = height of the object.
Let's say that, at the bottom of the slope, the height if 0m. That means the height of the object, the sled, is h = 2m. We are also told that the mass of the sled is m = 45kg and that g = 9.8 m/s^2.
Plug these values into the equation for potential energy:

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Answer: 822 J