Question.3779 - Go to the University of Colorado Boulder website and select the Energy Skate Park: Basics simulation (https://phet.colorado.edu/en/simulation/energy-skate-park-basics). You can activate it right in the window by clicking on it. You can also download to your computer if you wish. Start in the Introduction tab. You will observe the energy of a skateboarder. Start with the U-shaped track (should be the first one). It may be helpful to set the speed at the bottom to slow motion. Which part(s) of the ramp would potential energy be greatest? How about kinetic energy? In the U-shaped ramp, both highest points will experience potential energy, while at the lowest points of the ramp, where the speed of the skater is high, kinetic energy is high. Select the speed box, the place the skater on the top of one side. Where is speed the highest and lowest? Does that make sense with your answer for #2? At the lowest point in the ramp is highest, while the speed is lowest at the top which both aligns with question 2 implying that potential energy tends to be converted to kinetic energy when skater moves downwards and up Suppose the skaters mass is 70 kg and starts at the top of one side, 10 m above the low point. Calculate her energy there. What will her total energy be at the top of the other side? How about at the low point? Potential energy = mgh = 70 x 9.81 x 10 = 6867 J at top of other sides, while at lowest point PE = 0 J, and KE = 6860 J Select the bar graph option. The right bar tells you what the total energy of the skater is. As the skater moves back and forth does this value change? total energy bar remains constant, experiencing the fluctuational conservation of energy in an idealized frictionless environment between potential and kinetic As the skater moves from one side of the ramp, to the low point, and to the other high point, how to the potential and kinetic energies change? Moving from a high point down to the lowest point, potential energy will experience a decrease while kinetic energy increases when the skater moves from higher point downwards to lowest point but on the other hand, kinetic energy decreases when moving back up and potential energy increases. Kinetic and potential energies changes as the skater moves, as noted in #6. How do potential and kinetic energies compare with the total energy graph? Is there any connection? As the total energy bar remains consistent, both potential and kinetic energy bars change inversely to each other dynamically proportional to movement of the skater, that implies conservation of total energy showing the interchange of potential and kinetic energies Change the mass to large. How does the total energy change? What if you change it to small? Since PE depends on the mass of the skater the total energy also increases directly proportionally, while decrease in mass decreases the total energy Switch the tab to Friction. Make sure friction is set to none. Start the skater at the top of the left part of the U-shaped ramp. Does she make it to the same height on the other side? Why or why not? Due to no friction, the skater reaches the same height on both sides due to conservation of energy Set friction to the middle then start the skater at the top left again. Does she make it to the same height on the other side? Why or why not? With friction acting the skater does not reach the same height and also friction dissipates thermal energy as heat in turn reducing the skaters total mechanical energy. Select the bar graph. What time of energy is friction related to? Where does this energy come from, rather, what energy converts to this energy? Lastly, during what part of the motion is the friction-energy increased the fastest? Due to increased friction acting on the skater, it converts the mechanical energy into thermal energy, particularly when at higher speeds kinetic energy is converted into thermal energy with friction acting on it Select the W-shaped ramp and keep everything already selected bring the skater to the upper left part and watch her go. Suppose the 70 kg skater starts on the top left at a height of 15 m. She skates down to the low point, up over the next small hill 5 m high, part way up the right side. Then she skates back down, barely over the small hill again, down again, and barely up the left hill. Does she make it over the small hill again? What energy did she have initially? What energy is required to reach the top of the small hill? If she cannot make it back up, how much energy must have been lost to friction? Starting from 15 m on the upper left, wherein pe = mgh = 70 x 9.81 x 15 = 10300.5 J, the?required energy to reach the 5 m hill top = pe = mgh = 70 x 9.81 x 5 = 3433.5 J; since the skater cannot make it back up, the difference between initial and current energy is the energy lost due to friction.

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