Different Reference Frames DO NOT AFFECT deltaU
I said this on the previous slide, but there's calculations here to back me up. On the left, we've got a model of Southmoore HS sitting on earth (not quite to scale.) My classroom, labeled Dowd, is on the second floor. On the left in blue, we take the zero point for potential energy to be the floor. A 1kg mass on the floor has 0J of energy. At 1m it has 9.8J and at 2m it has 19.6J. On the right in green, we take the zero point to be the floor the classroom below me. That makes the mass on my floor have a PE of 58.8 J, 1m up it has 68.6 J, and 2m up it has 78.4 J. In both cases, a mass moving from 2m above my floor to 1m above my floor has a deltaU of -9.8J. And that's all that matters. Our perspective is irrelevant to the mass's change in potential energy. On the right we have another picture of the reference frame that we use to describe potential energy changing as we move away from the earth.
Different Reference Frames DO NOT AFFECT deltaU
I said this on the previous slide, but there's calculations here to back me up. On the left, we've got a model of Southmoore HS sitting on earth (not quite to scale.) My classroom, labeled Dowd, is on the second floor. On the left in blue, we take the zero point for potential energy to be the floor. A 1kg mass on the floor has 0J of energy. At 1m it has 9.8J and at 2m it has 19.6J. On the right in green, we take the zero point to be the floor the classroom below me. That makes the mass on my floor have a PE of 58.8 J, 1m up it has 68.6 J, and 2m up it has 78.4 J. In both cases, a mass moving from 2m above my floor to 1m above my floor has a deltaU of -9.8J. And that's all that matters. Our perspective is irrelevant to the mass's change in potential energy. On the right we have another picture of the reference frame that we use to describe potential energy changing as we move away from the earth.