0442 Conservation of Energy Skatepark Practice

Will the skater make it past the first hill shown? Friction is turned off for the track shown above.

• Yes, because his potential energy will turn into kinetic energy to get him over the hill

• Yes, because the second hill is almost the same height as where he starts

• No, because the second hill is higher, so he doesn't have enough potential energy

• No, because his potential energy will turn into thermal energy, so he'll be too slow

Will the skater make it over the first hill? Friction is turned OFF.

• Yes, because the second hill is lower than his starting position, so some potential energy will be kinetic energy.

• Yes, because all of his potential energy will be kinetic energy at the second hill.

• No, because some potential energy will become thermal energy due to friction, leaving him with too little speed.

• No, because he won't have enough potential energy to make it over a hill.

Friction is turned to VERY HIGH. Will the skater make it over the next hill?

• Yes, because he starts higher than the first hill so he'll have some kinetic energy at the second hill.

• Maybe - Only if friction does not slow him down too much that he no longer has enough kinetic energy to make it.

• No - No matter what, friction will slow him down too much to make it over another hill

In the next moment, the Kinetic Energy part of the energy pie will increase. Which way will the skater move? Up or down the hill?

• Up the hill because potential energy increases when kinetic energy increases

• Up the hill because kinetic energy moves people up hills

• Down the hill because potential energy must decrease when kinetic energy increases

• Down the hill because kinetic energy is determined by the height

In the next moment, the Kinetic Energy part of the energy pie will increase. What will happen to the potential energy?

• Potential energy will DECREASE

• Potential energy will INCREASE

• Potential energy will NOT CHANGE

In the next moment, the Kinetic Energy part of the energy pie will increase. What will happen to the skater's speed?

• The speed will DECREASE

• The speed will INCREASE

• The speed will NOT CHANGE

Shown in the graph is a plot of kinetic energy (in green) and potential energy (in blue). There is no friction. The vertical line is when the skater has an equal amount of kinetic and potential energy. At which spot A - E would the skater's position match that vertical line on the graph (meaning, when would the skater have transferred half of her potential energy to kinetic energy, if she started at A)?

• A

• B

• C

• D

• E

• A

• B

• C

• D

• E

• A

• B

• C

• D

• E

• A

• B

• C

• D