59840FAF-727E-436A-91E8-B95CF45A9BAA.jpeg - DOW Page 2 of 3 O Physics 1A Solution 4 Problem 4 Revenge of the Elevator a The elevator falls downward and

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Unformatted text preview: DOW Page 2 of 3 O Physics 1A Solution 4 November 11, 2019 Problem 4: Revenge of the Elevator a) The elevator falls downward, and gravity acts in the downward direction, so the work is just the force of gravity x the distance moved: W = Fx d=925kg x 10m/s x 28.5m = 263625J b) All of this energy gets converted into kinetic energy: W = 263625J = AKE = m , v = V2 x 263625J/925kg = 23.87m/s c) We need to consider the whole energy now. There is no kinetic energy at the end, so AKE is zero. And we have to add the compression distance x to our height change. AKE + APE = 0 kx2 2 +mg(-(h + x)) =0 40000x2- 9250x - 263625 = 0 Using the quadratic equation, we can solve this to find x = 2.69 m. d) In this case, since the elevator is not accelerating, the forces on it must be balanced. Therefore: mg = kx x = my - 0.116m K Problem 5: Rollercoaster a) At each point, we know that all of the potential energy from the change in height, gets converted to kinetic energy, so we have mgAh = mv?/2 - v = v(2gAh). We can use this formula to find the speed at points 2, 3 and 4: 30 MacBook Pro C Q Search or type URL + o & 6 7 8 9 O E R T Y U O P D F G H C K...
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