Here is the Flipping Physics energy review video:
And here are the answers to the practice test:
- Top-right one
- a) 12000 J (11594 J) b) 190 N
- a) 2.2 m b) same height c) because there is no friction so track length irrelevant, only the height matters (work done against gravity is only in vertical direction)
- If you do this as only an energy problem: 150 m. But that seems ridiculous because it is. Momentum also needs to be conserved. We haven’t covered that yet, but if you do the problem properly you would get 2.2 m.
- W = F*d so: F = m*a (substitute in delta v over delta t for a) and d = Vavg * t. Once you substitute those expressions in it simplifies to the formula for kinetic energy.