MC	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

Indicate whether each statement is an example or not of valid science affecting human life by circling ïyesÍ for each example and ïnoÍ for each non-example.

1.	Yes	No	A car radiator removes heat from the engine.
2.	Yes	No	Scientists gather data about long-term weather patterns.
3.	Yes	No	Satellites in orbit transmit location coordinate signals to ground-based receivers.
4.	Yes	No	Copper bracelets are sold to relieve pain.
5.	Yes	No	Manufacturers produce more efficient batteries.
6.	Yes	No	Water filters that enhance waterÍs nutritional value.
7.	Yes	No	Physicists collide subatomic particles in a lab.
8.	Yes	No	Magnetic insoles in shoes improve your health.
9.	Yes	No	False colored contact lenses change eye-color.
10.	Yes	No	Materials engineers research stronger light-weight materials.
11.	Yes	No	Dams are used to produce electricity.
12.	Yes	No	Dams create lakes used for recreational activities.
13.	Yes	No	Homes have indoor plumbing.
14.	Yes	No	More powerful batteries keep getting smaller.
15.	Yes	No	Fluorescent lights produce the same light with less power.

Correct Answers:

1.	Yes		A car radiator removes heat from the engine.
2.	Yes		Scientists gather data about long-term weather patterns.
3.	Yes		Satellites in orbit transmit location coordinate signals to ground-based receivers.
4.		No	Copper bracelets are sold to relieve pain.
5.	Yes		Manufacturers produce more efficient batteries.
6.		No	Water filters that enhance waterÍs nutritional value.
7.	Yes		Physicists collide subatomic particles in a lab.
8.		No	Magnetic insoles in shoes improve your health.
9.	Yes		False colored contact lenses change eye-color.
10.	Yes		Materials engineers research stronger light-weight materials.
11.	Yes		Dams are used to produce electricity.
12.	Yes		Dams create lakes used for recreational activities.
13.	Yes		Homes have indoor plumbing.
14.	Yes		More powerful batteries keep getting smaller.
15.	Yes		Fluorescent lights produce the same light with less power.

MC	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

A young girl is swinging in a backyard swing. As she moves through the lowest point of her swing, she has reached her

a. minimum KE

b. maximum KE

c. maximum PE

d. none of the above

Correct Answer: b

MC	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

The law of conservation of energy implies that:

a. Potential and Kinetic energy are always completely changed to useful work.

b. The total energy of a system remains constant, if all forms of energy are considered.

c. Losses do not occur when energy is converted from one form to another.

d. All heat energy is wasted.

Correct Answer: b

I	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

A popular ride at the local amusement park is the log flume. In this ride the rider is placed in a boat designed to resemble a large log. The log with riders is moved along a water way until it is taken to the top of an incline. From the top of the incline the log is released. At the bottom of the incline the log returns to the water way from which the ride originated.

Answer the following questions.

1. Describe the total energy of the boat at each of the stages of the ride listed below.

a. Point A, stopped for loading.

b. Point B, moving at constant speed on the course.

c. Point C, moving up the incline at constant speed.

d. Point D, moving down the incline at increasing speed.

e. Point E, at the bottom of the incline before stopping.

f. Point F, stopped to unload.

2. Where did the every come from, where did it go?

Correct Answers:

1. Total energy: (1 point for each answer a-f)

a. Stopped for loading, zero energy.

b. Placed in uniform motion, kinetic energy (KE):

KEnergy = (1/2)mv²

c. Moving up the incline at constant speed, kinetic energy plus increasing potential energy (PE = mgh) as it moves to top.

d. Moving down incline at increasing speed. Increasing kinetic energy and decreasing potential energy.

e. At bottom of incline. Maximum kinetic energy, potential energy zero.

f. Stopped to unload, zero energy.

2. Energy source:

Energy came from mechanical device to start the boat moving and to move the boat up the incline. (1 point)

Energy was given up to the water at the bottom of the incline as the water absorbed the energy of the boat. (1 point)

E	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

Dams are a common means of controlling water flow and producing electricity. Explain the benefits, uses, and potential harm caused by damming rivers. How does this practice affect human and non-human life? You do not need to state your opinion. Be thorough in your analysis, and include both positive and negative factors. You will be graded on the completeness of your explanations as well as basic grammar and spelling.

Correct Answers:

Complete answers should include, but may not be limited to:

Positive

1. Electricity for homes, business, and manufacturing.

2. No obvious pollution.

3. Water used for recreational activities.

4. Water used for drinking and/or irrigation.

5. Provides additional habitat for aquatic life.

Negative

1. Destroys habitat in the flood basin.

2. Silt and other forms of pollution not seen.

3. Increased evaporation.

4. Erosion downstream.

5. Potential for dam failure and potential flood.

E	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

As population grows, demand for electricity also grows. Scientists are working on alternative, renewable sources of energy. Until such sources are more readily available, we will have to build more traditional power plants to keep up with rising demand.

Suppose your community is asked to vote on one of two types of power plants„coal or nuclear. Write three paragraphs about which type of power plant you would vote to build. Be sure to include the advantages and disadvantages of each type, and explain why you would prefer one to the other.

Scoring Guide:

Students should include the following:

• Select one of the two types of power plants they would vote for.
• Describe advantages and disadvantages of each type, which may include the following:

	Advantages	Disadvantages
Nuclear	Ample supply of fuel	Fear of nuclear accident
	Clean, no air pollution	Nuclear waste produced
		Higher security required (potential terrorist threat)
Coal	Coal is plentiful in Utah	Pollution of air
	Coal is relatively inexpensive	Mining some wilderness areas will destroy habitat
		Large amounts of coal are required

• Support their stated position as to which type to vote for. Explain why they feel one type is preferable to the other.
• Correct spelling, punctuation, and grammar. At least three paragraphs.

P	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

One reason speed limits are imposed throughout the country is because a as a car goes faster its required breaking distance increases dramatically. Draw a graph of braking distances versus speed and label the relationship as inverse, parabolic, or linear.

KE = W 1/2mv² = Fd d = kv²

Velocity mi/hr	Stopping distance
10	10
20	40
30	90
40	160
50	250
60	360
70	490

Scoring Guide:

2 points for correct graph

1 point for correct relationship

Correct Answer:

P	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

A 10 kg rifle is fired. As the 25 g bullet travels through the barrel, it loses 400J of thermal energy. Neglecting the surroundings, how much thermal energy is gained by the barrel?

Correct Answer: 400 J

P	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

An 8.0 kg ball is dropped from a height of 28 m above the ground. The ball bounces to a height of 22 meters on the first bounce.

1. How much energy was lost?

2. How fast was the ball moving as it left the ground on the first bounce?

3. Where did the energy go?

4. When the ball is still 11 m from the ground (after the first bounce) what part of its energy is potential energy and what part is kinetic energy?

Correct Answers:

1. Potential energy = (mass)(acceleration of gravity)(height)

(8.0 kg)(9.8 m/s²)(28 m) = 2195.2 joule (energy started with) (1 point)

Energy at 22 m high = (8.0 kg)(9.8 m/s²)(22 m) = 1724.8 joule (1 point)

Energy lost = 2195.2 j Æ 1724.8 j = 470.4 j (1 point)

2. Kinetic energy as it leaves the ground equals the potential energy at highest point. (1 point)

Kinetic energy = (1/2) m v²

1724.8 j = (1/2) (8.0 kg) v², v² = 1724.8 / (1/2)(8.0) = 431.2 m²/s²

velocity = square root (431.2) = 20.8 m/s (1 point)

3. Some energy was converted into heat both in the ball and in the ground. Some energy became sound energy. (1 point)

4. At 11 meters above the ground the potential energy is (8.0 kg)(9.8 m/s²)(11 m) = 862.4 J. The total energy as the ball left the ground is the same as the total energy at its highest point after bouncing (1724.8 joule).

Total energy - potential energy = kinetic energy

1724.8 j Æ 862.4 j = 862.4 j (1 point)

Or: At 11 m it has half of the potential energy it will have at 22 m. The rest of the energy must be kinetic energy. Half of the total energy is potential and half is kinetic. 862.4 j for each.

P	Physics	Standard: 04
Objective: 02. Describe conservation of energy in terms of systems.
ILO:

An airplane drops 400 m to escape some freezing rain. If it maintained the same speed but lost 200,000,000 J of energy:

1. How much PE did it lose?

2. How much KE did it lose?

3. What is the planeÍs mass?

4. Since the total energy of the system doesnÍt seem to be conserved, explain where the 200,000,000 J went.

Correct Answers:

1. 200,000,000 J

2. 0 J

3. 51,000 kg

4. Air friction

Scoring Guide:

1 point for each correct answer

Total: 4 points