Match each word to the sentence where it best fits.
| system | | law of conservation of energy | | open system | | closed system | | state | |
- The ________ says that energy stays constant over time.
- We choose the objects and influences in a/an ______ to focus on what we are trying to investigate and exclude things that are irrelevant.
- A particular configuration of all the elements in a system is its _______.
- A/An ________ is one in which energy can flow into or out of it over time.
- A/An ________ is one in which there is no net flow of energy into or out of it.
| friction | | efficiency | | work–energy theorem | |
- The _______ of a system describes how effectively the system transforms input energy into output energy.
- The amount of work you do on a basketball is converted to its energy of motion through the _______.
- When a car rolls down a ramp, not all of the potential energy becomes kinetic energy because ______ transforms some energy into heat and wear.
- According to physics, energy can never be created or destroyed and the energy content of the universe is constant. So why are smart people worried about “conserving energy lest we run out”?
- Ask two friends the meaning of the word “conservation” in each of the following sentences.
Sentence 1: “Potential and kinetic energy obey a conservation law that applies to all physical processes.”
Sentence 2: “Many towns practice ecological conservation by keeping certain areas of land wild and undeveloped.”
| | - Your friend brags that his ball can bounce to a higher height than it was initially dropped from. Is he telling the truth?
 A roller coaster car begins at rest at the top of the first hill. Draw a sketch of a roller coaster with a second hill where the roller coaster cannot reach the top. Draw a sketch of a different roller coaster with a second hill that the roller coaster can get over.
- A bowling ball and a tennis ball are dropped separately in such a way that both have the same kinetic energy when they hit the ground. Were they dropped from the same height or a different height? If the latter, which one was dropped from a higher point?
- Give a five-slide oral presentation describing the difference between the law of conservation of energy and the everyday use of the term “energy conservation.”
- You are at an amusement park to conduct a field investigation.
- How can you estimate the maximum height of a roller coaster if you are only given a radar gun?
- Alternatively, your teacher wants you to use the roller coaster to demonstrate energy conservation, and she allows you to use both a radar gun and a meter stick. Explain how you would demonstrate energy conservation.
 Two balls are dropped, one from twice the height of the other. What is the ratio of the speeds each ball reaches when they hit the ground?
- From a roof, you throw three equal-mass balls each with the same initial speed: one straight down at the ground, the second straight up, and the third horizontally out from the building. When each of the three balls hit the ground, which one has the most kinetic energy?
- A bucket of sand is dropped several meters onto a lever that launches a ball upward.
- What should be included in the system you choose to apply energy conservation to find the height the ball reaches?
- Is the system open or closed?
- What might make the approximation of a closed system inaccurate?
- How would an open system affect the height the ball reaches compared to an ideal closed system?
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