Winnetonka 9th Grade Physics: Unit 10 test

Energy

𝐄𝐟𝐟𝐢𝐜𝐢𝐞𝐧𝐜𝐲   =  𝐖𝐨𝐫𝐤  𝐎𝐮𝐭𝐩𝐮𝐭𝐖𝐨𝐫𝐤  𝐈𝐧𝐩𝐮𝐭

𝑬𝒈  =  𝐦𝐠𝐡 𝑬𝒌  =  𝟎. 𝟓𝐦𝒗𝟐  g  =  9.8  m/s/s    

Describe how electromagnetic energy is transferred through space as electromagnetic waves of varying wavelength and frequency A B

C D

1. Which one of the waves above has the longest wavelength?

A A B B C C D D

2. Which one of the waves above has the highest frequency?

A A B B C C D D

3. Based upon the waves above, which wave is likely to be a gamma wave?

A A B B C C D D

4. Microwave radiation can pass through glass. To protect us there is a mesh screen. What size must the holes be to protect us AND also allow us to see our food?

A Buildings B Humans C Pinhead D Atomic Nuclei

5. Select the statement below that accurately distinguishes electromagnetic waves from mechanical waves. A. Electromagnetic waves and mechanical waves can move through a vacuum B. Mechanical waves must transmit energy through a medium while electromagnetic waves can transmit energy through a vacuum. C. Electromagnetic waves move matter. Mechanical waves move sound. D. Electromagnetic waves and mechanical waves are the same in every way. Identify stars as producers of electromagnetic energy 6. Which body emits visible electromagnetic waves? A. Both the Sun and the Earth. B. Only the Earth. C. Only the Sun. D. Neither the Sun or the Earth. 7. What is the reaction that is responsible for all of the energy reaching Earth from the sun?

A. Chemical reaction B. Chain reaction C. Nuclear fission reaction D. Nuclear fusion reaction

8. What part of a star’s life cycle gives off the most electromagnetic radiation? A. Supernova

B. Stellar Nebula C. White Dwarf D. Red Giant

9. During the life cycle of a star, it’s fuel converts the one element to another. Using the periodic table above, which element would not be involved because the star supernovas before it can be reached?

A. Co B. Mn C. O D. H Identify the role of nuclear energy as it serves as a source of energy for the Earth, stars and human activity (e.g., source of electromagnetic radiation, thermal energy within mantle, nuclear power plants, fuel for stars) 10. The Sun continuously radiates energy into space, some of which is intercepted by the earth. The average temperature of the surface of the earth remains about 27 degrees Celsius. Why doesn’t the earth’s temperature rise as it intercepts the sun’s energy?

A The earth reflects the sun’s light. B The earth radiates an amount of energy into space equal to the amount it

receives. C The energy only raises the temperature of the upper atmosphere and never

reaches the surface. D The thermal conductivity of the earth is low.

11. What reaction is responsible for energy produce by a nuclear power plant? A. Chemical reaction B. Chain reaction C. Nuclear fission reaction D. Nuclear fusion reaction 12. The Sun and nuclear power plants on Earth both use nuclear reactions to create energy. Which of the following statements below is true? I. The Sun conducts nuclear fusion. II. The Sun conducts nuclear fission.

III. Nuclear power plants conduct nuclear fusion. IV. Nuclear power plants conduct nuclear fission. A. I and III B. I and IV C. II and III D. II and IV Describe the transfer of energy that occurs as energy changes from kinetic to potential within a system (e.g., car moving on rollercoaster track, child swinging, diver jumping off a board) 13. How can you increase an object’s gravitational potential energy?

A. Increase the object’s velocity B. Decrease the object’s velocity C. Increase the height of the object’s position D. Lower the height of the object’s position

14. How can you decrease an object’s kinetic energy?

A. Increase the object’s velocity B. Decrease the object’s velocity C. Increase the height of the object’s position D Lower the height of the object’s position

15. A bowler releases a bowling ball at 5 m/s. The ball speeds up as it rolls down the ramp to the pins. Select the correct statement about the energies present at A, B or C.

A. A: EK= 0 and EGRAV > 0

B: EK > 0 and EGRAV > 0 C: EK > 0 and EGRAV > 0

B. A: EK = 0 and EGRAV = 0

B: EK < 0 and EGRAV > 0 C: EK > 0 and EGRAV > 0

C. A: EK > 0 and EGRAV > 0

B: EK > 0 and EGRAV > 0 C: EK > 0 and EGRAV > 0

D. A: EK > 0 and EGRAV > 0

B: EK > 0 and EGRAV > 0 C: EK > 0 and EGRAV = 0

16. At position A, the roller coaster car has 1000J of gravitational potential energy, comparing position A to position B. Which statement below concerning the energy transformation for position B would be true?

A. The car at position B has 1000J of gravitational energy and 1000J of kinetic energy. B. The car at position B has1000J of Kinetic energy and 0J of gravitational potential energy. C. The car at position B has 1000J of gravitational energy and 0J of kinetic energy.

17. Where is the does the pendulum’s energy distribution match the Energy Pie Chart at the right?

A. At positions 1 and 5 B. At position 3 only C. At positions 2 and 4 D. At positions 2 and 5

Compare the efficiency of systems (recognizing that, as work is done, the amount of usable energy decreases) 18. A solar cell needs 800 J of input energy to produce 200 J of output energy. What is it efficiency?

A. 400% B. 16% C. 25% D. 10%

19. One way to improve the efficiency of a machine is to

A. decrease the friction. B. increase the friction. C. none above

20. Each second, a nuclear power plant generates 2000 MJ of thermal energy from nuclear reactions in the reactor’s core. This energy is used to boil water and produce high-pressure steam at 300 degrees Celsius. The steam spins a turbine, which produces 700 MJ of electric power, then the steam is condensed and the water is cooled to 30 degrees Celsius before starting the cycle again. What is the plant’s efficiency? A. 4.28% B. 15% C. 35% D. 10% 21. Hybrid vehicles are powered by a gasoline engine paired with an electric motor and batteries. They get much better mileage in the stop and go of city driving than conventional vehicles do. When you brake to stop in a conventional car, friction converts the kinetic energy of the car’s motion into thermal energy in the brakes. In a typical hybrid car, some of this energy is converted into chemical energy in a battery. Which statement below best explains how this makes a hybrid vehicle more efficient? A. When energy is transformed into thermal energy, the energy becomes available for the car. B. In a hybrid car, the kinetic energy becomes irreversible energy and cannot be use by the car. C. In a hybrid car, the thermal energy is converted into chemical energy in the battery, when the car starts again the chemical energy transforms back into kinetic energy. D. In a hybrid car the brakes produce less friction. 22. You see an advertisement for a new free fall ride at an amusement park. The ride is 50 meters tall, has a mass of 100kg, and reaches a speed of 28 m/sec at the bottom. How efficient is the ride?

A. 125% B. 178% C 80% D. 55%

Classify the different ways to store energy (i.e., chemical, nuclear, thermal, mechanical, electromagnetic) and describe the transfer of energy as it changes from kinetic to potential, while the total amount of energy remains constant, within a system (e.g., using gasoline to move a car, photocell generating electricity, electromagnetic motor doing work, energy generated by nuclear reactor) 23. The gasoline in a car’s combustion engine is a form of:

A. Nuclear energy B. Thermal energy C. Radiant energy D. Chemical energy

24. The mechanical energy that is associated with motion is?

A. Kinetic energy B. Potential energy C. Radiant energy D. Chemical energy

25. Using the figure above to predict the gravitational and kinetic energy at position C? A. Half Kinetic energy and half Gravitational Potential energy B. All Gravitational Potential energy C. All Kinetic energy

The energy requirements of United States are met by a variety of sources as shown in the chart above. Biomass, solar, wind and geothermal power are combined under the category labeled ‘other’. Use the graph above to answer questions 4 and 5. 26. What percentage of US energy comes from renewable energy sources?

A. 100% B. 68% C. 32% D. 13%

27. The rechargeable batteries of an electric car must be replenished by power from the electric grid. Choose the statement below that most accurately describes an advantage of an electric car (reference the graph above).

A. Electric cars consume 32% less fossil fuel than gasoline-powered cars. B. Electric cars do not consume fossil fuel, directly or indirectly. C. Electric cars have an unlimited range on a single charge. D. Energy is destroyed when the batteries of an electric car discharge.