1. DCAS Review of Energy Across the Systems

2. 1. Radio waves, visible light, and x-rays are examples of electromagnetic waves that always differ from each other in
A. amplitude
B. intensity
C. temperature
D. wavelength

3. D. wavelength
Electromagnetic waves are classified by their wavelength. Gamma rays have the shortest wavelength and radio waves have the longest. Visible light falls somewhere in the middle of the spectrum. The full range of the electromagnetic waves is called the electromagnetic spectrum.
The only part of the electromagnetic spectrum that you can see with your eyes is visible light. Visible light includes all the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. Red light has the longest wavelength; violet light has the shortest. When all the different colors of light are combined, you see them as white light.
ROYGBIV red orange yellow green blue indigo violet

4. 2. A sound wave can be transmitted through all of the following except
A. a gas
B. a liquid
C. a solid
D. a vacuum

5. D. Vacuum
Unlike light, sound waves need a medium (matter) to travel through. Sound cannot exist in a vacuum. Like light, sound travels at different speeds through different materials. In general , sound travels faster through solids than through liquids, and faster through liquids than through gases. Sound waves also travel faster through a warmer medium than through a cooler medium
Frequency is the number of waves produced in a given time. The frequency of a sound wave determines its pitch, or how high or low the sound is. The higher the frequency of a sound wave, the higher the pitch. Most humans can perceive sound waves within a frequency range of 20 to 20,000 Hz, or wave per second. .

6. 3. Heat energy is most closely associated with which one of the following?
A. gravitational potential energy
B. Kinetic energy
C. Light energy
D. Chemical energy

7. C. Light Energy

8. 4. Why does wearing a light colored shirt on a hot day feel cooler than wearing a dark colored shirt?
A. White objects absorb all visible light and dark objects reflect all visible light
B. Both white and dark objects reflect all visible light
C. White objects reflect all visible light, where black objects absorb all visible light
D. Both white and dark objects reflect all visible light

9. C. White objects reflect all visible light, where black objects absorb all visible light

10. 5. Two oppositely charged objects are separated by a small distance
5. Two oppositely charged objects are separated by a small distance. The objects are then moved three times farther apart from each other. Which of the following statements best describes what happens to the electrical force between the objects?
A. The force of attraction increases.
B. The force of attraction decreases.
C. The force of attraction becomes zero.
D. The force of attraction stays the same.

11. B. The force of attraction decreases.
Electric force and magnetic force are closely related. This is because both are caused by negative and positive charges in matter. Atoms, which make up all matter, contain a positively charged nucleus and a negatively charged cloud of electrons. When charges from one piece of matter interact with those of another piece of matter, they produce both electric and magnetic forces. These forces can be attractive (pulling the objects together) or repulsive (pushing the objects apart)
The electric force between two charged objects varies depending on the amount of charge on each object and the distance between them. The electric force between two objects is proportional to the product of the charges on the objects. If the charge on one object is doubled, the electric force between the objects will also be doubled, as long as the distance between the objects remains the same.
As you increase the distance between two charges, if everything else is the same, the electric force decrease the further they are apart. .

12. 6. X-ray waves and infrared waves are both electromagnetic waves
6. X-ray waves and infrared waves are both electromagnetic waves. Which of the following describes another property x-ray waves and infrared waves share?
A. Both waves are transverse.
B. Both waves have the same frequency.
C. Both waves have the same wavelength.
D. Both waves travel at the same speed in a vacuum.

13. A. Both waves are transverse.
When the oscillation (back and forth or up and down motion) of a wave is perpendicular to the direction in which the wave travels, the wave is called a transverse wave. The peak, or highest point, of a transverse wave is the crest. The valley, or lowest point, between the two crest is the trough. Electromagnetic waves and a secondary wave (S wave) are examples of transverse waves.
A longitudinal wave is a wave whose oscillation is parallel to the direction in which the wave travels. For example, if you set a spring on your desk and push the end of the spring over and over, you create regions where the coils are closer together (compressions) and regions where the coils are farther apart (rarefactions). The compressions and rarefactions move in the same direction in which the wave travels. Examples of longitudinal waves are sound waves and a type of seismic wave called a primary wave (P wave)

14. 7. A car with its horn sounding approaches a group of students
7. A car with its horn sounding approaches a group of students. Assume the car’s horn produces sound waves with a constant frequency.
Which of the following statements best explains why the students hear a higher pitch as the car approaches than when it is stopped?
A. The sound waves increase in speed as the car approaches the students.
B. The sound waves decrease in speed as the car approaches the students.
C. The sound waves are heard at a lower frequency as the car approaches the students.
D. The sound waves are heard at a higher frequency as the car approaches the students

15. D. The sound waves are heard at a higher frequency as the car approaches the students
The higher the frequency, the higher the pitch. When the car is coming toward you with its horn blowing, it gets louder the closer it gets to you. When the car is moving away from you, the lower the frequency and lower pitch.
If an ambulance is moving toward you, the sound waves from the siren are compressed in the direction of motion. The distance between the wave fronts is shortened, though the wave speed remains the same. The sound waves reach your ear at a higher frequency; they sound higher pitched than they would if the ambulance were at rest. If an ambulance is moving away from you, the frequency at which the waves reach your ear is less, and you hear the sound of the siren at a lower pitch than you would if the ambulance were not moving . This change in the observed frequency of a wave is called the Doppler effect.

16. 8. A 5 kg rock and a 10 kg rock are dropped from a height of 10 m on Earth. Which of the following statements describes what happens to the potential energy of the rocks?
A. Neither rock loses potential energy because no work is done on the rocks.
B. Both rocks lose the same amount of potential energy because they fall from the same height.
C. The 10 kg rock loses more potential energy than the 5 kg rock because the 10 kg rock falls faster.
D. The 10 kg rock loses more potential energy than the 5 kg rock because the 10 kg rock has more mass.

17. D. The 10 kg rock loses more potential energy than the 5 kg rock because the 10 kg rock has more mass.
Gravitational potential energy depends on both mass and height. Because it is caused by the force of gravity, gravitational potential energy near Earth depends on both the mass of the object and height of the object relative to Earth’s surface. If two objects of different masses are at the same height, the heavier object has more gravitational potential energy than the light one does.

18. 9. Which of the following statements is true according to the law of conservation of energy?
A. Energy cannot be created
B. Energy cannot be destroyed
C. Energy can be converted from one form to another
D. All of the above

19. D. All of the above

20. 10. A large container of cold water is moved from a refrigerator to a table. A hot piece of metal is placed into the water. Which of the following best describes the final temperature of the metal?
A. higher than the final temperature of the water
B. the same as the final temperature of the water
C. lower than the initial temperature of the water
D. the same as the initial temperature of the water

21. B. the same as the final temperature of the water

22. 11. Which of the following statements best describes the visible spectrum of light as seen by the human eye?
A. The lowest frequency appears red, and the highest frequency appears violet.
B. The lowest frequency appears red, and the highest frequency appears yellow.
C. The lowest frequency appears green, and the highest frequency appears violet.
D. The lowest frequency appears green, and the highest frequency appears yellow

23. A. The lowest frequency appears red, and the highest frequency appears violet.

24. .
12. The diagram above represents a bicyclist at the top of a hill with 4 points labeled W,X,Y and Z.
Assume that the bicyclist does not apply the brakes as he rides down the hill. At which point will the bicyclist’s kinetic energy be closest to zero?
A. point W
B. point X
C. point Y
D. point Z

25. A. Point W

26. 13. The diagrams below show a man swinging a golf club.
The kinetic energy of the golf club at point Y is more than the potential energy of the
club at point X. Which of the following statements best explains why this fact does not
violate the law of conservation of energy A
A. Gravity is constant from point X to point Y.
B. Air resistance is greater at point Y than at point X.
C. Acceleration due to gravity is greater at point Y than at point X.
D. Energy is added by the man to the golf club from point X to point Y.

27. D. Energy is added by the man to the golf club from point X to point Y.

28. 14. A student swings a bat horizontally, making contact with a ball thrown to her. The ball leaves the bat, and the bat continues moving through the rest of the swing.
Which of the following statements describes the change in energy necessary to do work on the ball?
A. All the kinetic energy of the bat is converted to work.
B. All the potential energy of the bat is converted to work.
C. Some of the kinetic energy of the bat is converted to work.
D. Some of the potential energy of the bat is converted to work

29. C. Some of the kinetic energy of the bat is converted to work

30. 15. Two wave forms traveling through a substance are depicted below
15. Two wave forms traveling through a substance are depicted below. Wave A has twice the frequency of Wave B, but Wave B has twice the amplitude of Wave A. Which wave can deliver the greatest amount of energy every second?
A. Wave A can deliver more energy
B. Wave B can deliver more energy
C. Both waves can deliver the same amount of energy
D. Can’t be determined

31. C. The same
The amplitude of a wave is the distance a wave oscillates from its resting position. The larger the amplitude, the more energy carried by the wave.
Wavelength is the distance from any point on one wave to a corresponding point on an adjacent wave.
Frequency is the number of oscillations produced in a certain amount of time. The greater the number of oscillation per second, the higher the frequency . The higher the frequency, the more energy carried by the wave.

32. 16. The sequence of energy changes shown in the diagram (energy chain) best explains with event?
A. a flashlight is on
B. a candle burns
C. gasoline burns to propel a car
D. electric energy runs a refrigerator

33. C. Gasoline burns to propel a car

34. 17. Which of the following is an example of an object with elastic potential energy?
a wind-up toy that has been wound up b.
a compressed basketball c.
a stretched rubber band d.
all of the above

35. D. All of the above
An object gains a different type of potential energy when it is stretched. The potential energy associated with objects that can be stretched or compressed is called elastic potential energy. The energy stored in a stretched object, such as a bow, rubber band or spring, is elastic potential energy.