Energy transformations Sources and Effects and transmission of Energy

Transcription

1 Winnetonka 9 th Grade Physics: Unit 9 test Energy transformations Sources and Effects and transmission of Energy Kinetic Energy: E! =!! m v! Gravitational Potential Energy: E! = m g h Elastic Potential Energy: E!" =!! k x! Work: W = F d Force due to Gravity (or weight): F! = m g

2 Relate kinetic energy to an object s mass and its velocity 1. A 2 kg ball and a 4 kg ball move to the right at the same constant speed. Select the statement below that describes how their kinetic energies compare. a. The more massive ball has twice the kinetic energy of the less massive ball. b. The more massive ball has half the kinetic energy of the less massive ball. c. The more massive ball has four times more kinetic energy than less massive ball. d. The more massive ball has four times less kinetic energy than less massive ball. 2. A red ball moves to the right at twice the speed of a blue ball. If the balls are the same mass, select the statement below that describes how their kinetic energies compare. a. The red ball has twice the kinetic energy of the blue ball. b. The red ball has half the kinetic energy of the blue ball. c. The red ball has four times more kinetic energy than the blue ball. d. The red ball has four times less kinetic energy than the blue ball. 3. A 700 kg sports car speeds down the road at 20 m/s. What is the Kinetic Energy of the sports car? a. 280,000 Joules b. 28,000 Joules c. 140,000 Joules d. 14,000 Joules 4. A 40 kg cart increases velocity from 3 m/s to 6 m/s. Select the statement that describes the effect on Kinetic Energy. a. E K of the cart will remain constant since the mass stays the same. b. E K of the cart will increase by 3 joules. c. E K of the cart will quadruple. d. E K of the cart will triple.

3 5. A moving 10 kg ball has kinetic energy of 45 joules. After 2 seconds, the kinetic energy of the ball is 90 joules. Select the statement that describes the motion of the ball. a. The ball has accelerated. b. The ball has maintained a constant velocity. c. The ball has maintained a constant mass. d. The ball has maintained a constant energy. Relate an object s gravitational potential energy to its weight and height relative to the surface of the Earth 6. The Gravitational Potential Energy of a red ball is greater than the Gravitational Potential Energy of a blue ball. If the red and blue balls have the same mass, select the statement(s) that must be true: I. The red and blue balls are located in the same gravitational fields and are located at different heights above the ground. II. The red and blue balls are located in different gravitational fields and are located at the same height above the ground. III. The red and blue balls are located in the same gravitational fields and are located at the same height above the ground. a. I only b. II only c. III only d. I and II only e. II and III only 7. A pair of skydivers jump from an airplane when the plane achieves an altitude of 10,000 feet. If Earl s gravitational potential energy is greater than Javon s immediately after they jump, select the statement that must be true. a. Earl and Javon have the same mass so their terminal velocities will be the same. b. Earl has more mass than Javon. c. Earl has less mass than Javon. d. Earl falls faster than Javon since he has more mass.

4 8. The path of a bouncing ball is shown above. The mass of the ball is 0.3 kg. If the initial height (h 0 ) of the ball is 5 meters, select the most likely values for the Gravitational potential energy of the ball at h 1 and h 2. a. At h 1, E g = 15 joules At h 2, E g = 10 joules b. At h 1, E g = 150 joules At h 2, E g = 100 joules c. At h 1, E g = 10 joules At h 2, E g = 5 joules d. At h 1, E g = 100 joules At h 2, E g = 50 joules Distinguish between examples of kinetic and potential energy (i.e., gravitational, elastic) within a system 9. Examine the path of a bouncing ball above. Examine the statements about the energy transfers between E k, E g and E el at points A, B, C and D. a. I and II only. b. I and IV only. c. II and III only d. I and III only I. At A, E K is at its maximum value. II. At A, E g is at its maximum value. III. At B, E el is at its maximum value. IV. At B, E g is at its maximum value. 10. A ball rests at the top of a 1 meter tall ramp. The 2 kilogram ball begins rolling down the ramp. If the ball and ramp are a closed system, what is the energy of the system? a. 2 joules b. 20 joules c. 200 joules d joules

5 11. When an object is moving, the energy due to its motion is: a. Elastic energy b. Dynamic energy c. Kinetic energy d. Mechanical energy 12. When an object changes shape, the energy due to its deformation is: a. Elastic energy b. Dynamic energy c. Kinetic energy d. Mechanical energy Describe the effect of work on an object s kinetic and potential energy 13. A compressed spring stores 500 joules of energy. How much work was done on the spring to store the energy? a. 0 joules b. 250 joules c. 500 joules d joules 14. A 20 newton crate is lifted 4 meters above the floor. How much work was done on the crate? a. 0 joules b. 40 joules c. 80 joules d. 800 joules

6 15. A 20 newton crate is lifted 4 meters above the floor. How much more gravitational potential energy does the crate have after it was lifted? a. 0 joules b. 40 joules c. 80 joules d. 800 joules 16. An 8 kg cart begins moving from rest. After 160 joules of work is done by the cart s motor, what is the final velocity of the cart? a. The final velocity of the cart is 10 meter after 160 joules of work is done on the system. b. The final velocity of the cart is 20 meters after 160 joules of work is done on the system. c. The final velocity of the cart is 10meters after 160 joules of work is done on the system. d. The final velocity of the cart is 20 meters after 160 joules of work is done on the system. Describe sources and common uses of different forms of energy: chemical, nuclear, thermal, mechanical, electromagnetic 17. When fossil fuels are burned or food is digested, energy is released. a. Mechanical energy b. Thermal energy c. Chemical energy d. Molecular energy 18. Geothermal energy creates spectacular displays when this energy is released through the earth s crust through volcanic activity. The source of the Earth s geothermal energy is a. Chemical energy b. Nuclear energy c. Mechanical energy d. Electromagnetic energy

7 19. Electromagnetic energy is a combination of: a. Electricity and magnetic poles b. Electric fields and magnetic fields c. Virtual electric and mechanical magnetic sources d. Electron and graviton energies Identify and evaluate advantages/disadvantages of using various sources of energy (e.g., wind, solar, geothermal, hydroelectric, biomass, fossil fuel) for human activity 20. Non-renewable sources of energy include: a. Fossil fuels b. Biomass c. Hydropower d. Wind 21. Depletion of the Earth s protective ozone layer is contributing to warming global temperatures. To slow the damage to the ozone layer, alternative energy sources must be used to reduce consumption of: a. Solar energy b. Biomass c. Fossil fuels d. Geothermal energy 22. The atom shown on the left below, splits into smaller atomic particles. When an atom is split, this process is called: a. Nuclear energy transformation b. Creation of thermal energy c. Nuclear fission d. Atomic division

8 23. The image above shows various energy resources sorted into group A and group B. Select the statement below that best describes this grouping. a. The costs of resource group A exceed the costs of resource group B. b. The environmental impact of resource group B exceeds that of resource group A. c. Resource group B represents renewable resources. d. Resource group A represents renewable resources. Describe the effect of different frequencies of electromagnetic waves on the Earth and living organisms (e.g., radio, infrared, visible, ultraviolet, gamma, cosmic rays) 24. The Earth s atmosphere and magnetic field deflects some of the Sun s electromagnetic energy. Select the electromagnetic wave frequencies that do reach Earth s surface. a. Radio waves, gamma waves, visible light waves b. Cosmic ray waves, visible light waves, radio waves c. Visible light waves, radio waves, microwaves d. Radio waves, visible light waves 25. Electromagnetic waves with can cause damage to human tissues. a. Short wavelength, high frequency, high energy b. Short wavelength, low frequency, high energy c. Long wavelength, low frequency, high energy d. Long wavelength, high frequency, low energy