Download Energy Exam Review KEY

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Name:
Learning Target 1: I can describe the different forms of potential and kinetic energy.
1. List three forms of energy and give an example of each of them.
Mechanical – a car; pedaling a bike
Chemical – food; things that burn
Heat (thermal) – a cup of coffee warming your hands
Electromagnetic (EM) – light, microwaves, radio waves
Nuclear – using uranium in a nuclear power plant
2. List the correct energy transformations as a radio is plugged in and turned on.
Electricity (EM ) powers the radio receiver, which in turn sends a signal to the speaker (EM); the speaker
produces a sound (mechanical)
3. List the correct energy transformations as a car is started and is driven across town.
Gasoline (stored chemical energy) is burned in the engine (chemical), which produces heat (thermal), which
drives the pistons (mechanical); which moves the car (mechanical)
Learning Target 2: I can describe the Law of Conservation of Energy (aka- 1st Law of Thermodynamics)
4. An apple is eaten. How does the energy of the apple compare to the energy stored and used by the person
eating it?
Assuming no loss, the energy of the apple will equal the energy stored and used by the person; however, in
reality, it requires some of that energy for the process of eating it and storing it in the body (and to later
release the energy)
5. What does it mean to say that that in all processes entropy (disorder) increases?
With every process, some energy gets lost (usually to heat) because there is always friction present
6. The Law of Conservation of Energy says that energy is neither created nor destroyed, but merely changes
form. Explain how this is shown by the motion of a roller coaster.
The energy that the cars use to make their way up and down the hills all over the coaster come from that first
big hill, and the energy is constantly being converted from potential to kinetic and kinetic to potential
mechanical energy as the cars go through route on the tracks.
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Learning Target 3: I can calculate the total Energy of a system by adding the Potential Energy and Kinetic Energy.
7. a. A toy car with a mass of 4 kg at rest has the same kinetic energy as a toy car with a mass of 8 kg at rest.
Why?
Because KE = ½ mv2; if velocity is zero, then KE equals zero, no matter the mass
b. What would happen to the kinetic energy of a 4 kg car if it were moving faster than another 4 kg car?
Then the KE of the car will increase according to KE = ½ mv2
8. If the roller coaster has 13,000 J of potential energy while at rest at the top of the first hill, how much kinetic
energy will it have at point Z if it has 1,200 J of potential energy at
that point (assume no friction)?
The total energy equals the potential energy plus kinetic energy,
so the total energy at the top is 13,000 J (KE = 0 + PE = 13,000 J).
With no friction, all but 1,200 J of PE has converted to KE. So, KE =
11,800 J (13,000 J – 1,200 J = 11,800 J).
9. Using the same data and picture above, how much PE and KE will the car have at point Y if point Y is half the
height of the first hill?
Being at half the height would mean the PE is half as much, 6,500 J (13,000 J/2 = 6,500 J). That “lost” PE of
6,500 J has converted to KE.
Learning Target 4:I can plan and conduct an investigation that provides evidence that the thermal energy transfer moves
toward equilibrium.
10. Heat travels from warmer objects to cooler objects. How does this impact your home on a hot day and your
air conditioner breaks? How will the heat move regarding outside and inside the home?
Heat from outside the home tends to travel to cooler areas, such as inside your home. Normally, the air
conditioner works to take the heat inside the home and move it to the outside, something it normally
wouldn’t want to do. If the AC breaks, heat will move from warmer areas to cooler areas.
11. If temperatures of a system tend to reach equilibrium, what will happen to the temperature of a 30 degree
block of ice placed in a 71-degree storage room?
The temperature of the block of ice will increase and the temperature of the storage room will decrease. The
temperatures will move closer to each other until they are the same temperature. (Because the room is likely
larger and warmer, the equilibrium temperature will likely be above freezing, so there will be a puddle of
water at the new room temperature.)
12. What will happen to the temperature of the storage room in the question before?
The temperature will be lower than it was before.
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People Search Review
Name:
Learning Target 1: I can describe the different forms of potential and kinetic energy.
1. List three forms of energy and give an example of each of them.
2. List the correct energy transformations as a radio is plugged in and turned on.
3. List the correct energy transformations as a car is started and is driven across town.
Learning Target 2: I can describe the Law of Conservation of Energy (aka- 1st Law of Thermodynamics)
4. An apple is eaten. How does the energy of the apple compare to the energy stored and used by the person
eating it?
5. What does it mean to say that that in all processes entropy (disorder) increases?
6. The Law of Conservation of Energy says that energy is neither created nor destroyed, but merely changes form.
Explain how this is shown by the motion of a roller coaster.
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Learning Target 3: I can calculate the total Energy of a system by adding the Potential Energy and Kinetic Energy.
7. a. A toy car with a mass of 4 kg at rest has the same kinetic energy as a toy car with a mass of 8 kg at rest. Why?
b. What would happen to the kinetic energy of a 4 kg car if it were moving faster than another 4 kg car?
8. If the roller coaster has 13,000 J of potential energy while at rest at the top of the first hill, how much kinetic
energy will it have at point Z if it has 1,200 J of potential energy at
that point?
9. Using the same data and picture above, how PE and KE will the car have at point Y if point Y is half the height of
the first hill?
Learning Target 4:I can plan and conduct an investigation that provides evidence that the thermal energy transfer moves
toward equilibrium.
10. Heat travels from warmer objects to cooler objects. How does this impact your home on a hot day and your air
conditioner breaks? How will the heat move regarding outside and inside the home?
11. If temperatures of a system tend to reach equilibrium, what will happen to the temperature of a 30 degree block
of ice placed in a 71-degree storage room?
12. What will happen to the temperature of the storage room in the question before?
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