Energy of Objects in Motion

Transcription

1 1 Energy of Objects in Motion Energy 1. Define Energy. 2. What are the two things necessary for work to be done on an object? 3. How can you determine the amount of work is being done on an object? 4. What would happen to an object s velocity if positive work is done on an object? 5. Based on the diagram below, is positive or negative work being done on the object? Explain. 6. Based on the graph below, is positive or negative work being done on the object? Explain. 7. A ball is dropped from the roof of the building. The ball initially had 100 J of Energy. Just as it landed it had 90 J or Energy. How much work was done on the ball as it fell? What did the work? 8. What are the two major forms of Energy? 9. What is the definition of Mechanical Energy? 10. What is the definition of Non-Mechanical Energy?

2 2 11. What would happen to an object s velocity if no work was being done on the object? 12. Based on the diagram below, is the object s speed increasing or decreasing due to Air Resistance. Explain in terms of work being done on the object. 13. Based on the graph below, which of the following is being done: positive work, negative work, no work. Explain. 14. At what time on the graph below does the object start to experience negative work being done on it? Explain. 15. An adult is driving a car which has 50 J of Energy. At the end of the drive the car still had 50 J of energy. How much work was done on the car during the drive?

3 3 16. What are the two forms of Mechanical Energy? 17. Name two forms of Non-Mechanical Energy. Kinetic Energy 18. What two factors does Kinetic Energy depend upon? 19. If an object is accelerating, how does its Kinetic Energy change? 20. If a mouse and an elephant have the same kinetic energy, can you determine which one is running faster? Explain. 21. If an object s speed is doubled, how does its Kinetic Energy change? 22. If the mass of an object is doubled, how does its Kinetic Energy change? 23. How much kinetic energy does an 80 kg man have while running at 3 m/s? 24. A 6 kg object has a speed of 20 m/s. What is its kinetic energy? 25. A 1000 kg car s velocity increases from 5 m/s to 10 m/s. What is the change it the car s kinetic Energy? 26. What is the SI unit for Kinetic Energy? 27. When is the only time that an object has no Kinetic Energy? 28. If an object is decelerating, how does its Kinetic Energy change? 29. If an object s speed is cut in half, how does its Kinetic Energy change? 30. If the mass of an object is cut in half, how does its Kinetic Energy change? 31. How much kinetic energy does a 4 kg cat have while running at 9 m/s? 32. A 2 kg watermelon is dropped from a roof and is traveling with a speed of 5 m/s just before it hits the ground. How much Kinetic Energy does the watermelon have at this moment? 33. A 700 kg horse is running with a velocity of 5 m/s. How much larger is the horse s Kinetic Energy compared to a 100 kg man running at the same speed? Gravitational Potential Energy 34. What three factors does Gravitational Potential Energy depend upon? 35. If an object is thrown up in the air, how does its Gravitational Potential Energy change? 36. If an object is falling, how does its Gravitational Potential Energy change? 37. How does your Gravitational Potential Energy change if you are placed on the moon where gravity is lower than on Earth?

4 4 38. If the mass of an object is cut in half, how does its Gravitational Potential Energy change? 39. A 1 kg ball is thrown up in the air and reaches a height of 5 m. What is its Gravitational Potential Energy at that moment? 40. A 200 kg boulder is sitting on top of a 10 m high hill. What is the boulder s Gravitational Potential Energy? 41. What is the gravitational potential energy of a 450 kg car at the top of a 25 m parking garage? 42. A 2.0 kg toy falls from 2 m to 1 m. What is the change in GPE? 43. A small, 3 kg weight is moved from a height of 5 m to a height of 8 m. What is the change in potential energy? 44. What is the SI unit for Gravitational Potential Energy? 45. When is the only time that an object has no Gravitational Potential Energy? 46. How does your Gravitational Potential Energy change if you are placed on Jupiter where gravity is larger than on Earth? 47. If the mass of an object is doubled, how does its Gravitational Potential Energy change? 48. A 75 kg skydiver is spotted at a height of 1000 m above the Earth s surface. How much Gravitational Potential Energy does the skydiver possess? 49. A placekicker in football is attempting a field goal and kicks a 0.75 kg football which hits the crossbar that is 3.1 m tall. How much Gravitational Potential Energy does the ball have when it hits the crossbar? 50. The Green Monster is the name for the left field wall at Fenway Park and is m tall. How much Gravitational Potential Energy does a 0.2 kg baseball have when it just clears the wall? 51. An 80 kg person falls 60 m off of a waterfall. What is her change in GPE? 52. A 0.25 kg book falls off a 2 m shelf on to a 0.5 m chair. What was the change in GPE? Elastic Potential Energy 53. What two factors does Elastic Potential Energy depend upon? 54. Define the term spring constant? 55. The same spring is stretched by 1 meter and then compressed by 1 meter. In which case will the spring have more Elastic Potential Energy stored in it? Explain. 56. Two identical springs are stretched. Spring A is stretched 1 meter while spring B is stretched 2 meters. Which spring will have more Elastic Potential Energy stored in it? Explain.

5 5 57. If a spring is stretched twice as far (as in #56), how many times larger is the Elastic Potential Energy that is stored in it? 58. A spring with a spring constant of 500 N/m is stretched 1 meter in length. How much Elastic Potential Energy does the spring have stored in it? 59. A spring with a spring constant of 250 N/m is stretched 0.5 meters. How much Elastic Potential Energy does the spring have stored in it? 60. A spring with a spring constant of 100 N/m is compressed by 0.25 meters. How much Elastic Potential Energy does it have stored in it? 61. Define the term Relaxed Length. 62. Two springs are stretched to the same distance. If spring A has a spring constant of 200 N/m and spring B has a spring constant of 400 N/m, which spring has more Elastic Potential Energy stored in it? Explain. 63. A spring with a spring constant of 100 N/m is not stretched. How much Elastic Potential Energy does the spring have stored in it? 64. A spring with a spring constant of 200 N/m is stretched 1 meter in length. How much Elastic Potential Energy does the spring have stored in it? 65. A spring with a spring constant of 500 N/m is compressed 0.5 meters. How much Elastic Potential Energy does the spring have stored in it? 66. A rubber band with a spring constant of 150 N/m is stretched by 0.25 meters. How much Elastic Potential Energy does it have stored in it? Conservation of Energy Questions refer to the diagram below 67. At which position does the block have maximum Gravitational Potential Energy? Explain. 68. At which position does the block have maximum Elastic Potential Energy? Explain.

6 6 69. At which position does the block have maximum Kinetic Energy? Explain. 70. At which position does the block have maximum Total Energy? Explain. Questions refer to the diagram below 71. At which position does the man have maximum Gravitational Potential Energy? Explain. 72. At which position does the man have maximum Elastic Potential Energy? Explain. 73. At which position does the man have maximum Kinetic Energy? Explain. 74. At which position does the man have maximum Total Energy? Explain. Questions refer to the diagram below 75. At which position does the ball have maximum Gravitational Potential Energy? Explain. 76. At which position does the ball have maximum Elastic Potential Energy? Explain. 77. At which position does the ball have maximum Kinetic Energy? Explain. 78. At which position does the ball have maximum Total Energy? Explain. Questions refer to the diagram below

7 7 79. At which position does the car have maximum Gravitational Potential Energy? Explain. 80. At which position does the car have maximum Elastic Potential Energy? Explain. 81. At which position does the car have maximum Kinetic Energy? Explain. 82. At which position does the car have maximum Total Energy? Explain. Types of Energy Resources 83. Define Renewable Resource. 84. Define Non-Renewable Resource. 85. List two examples of a Renewable Energy Resource. 86. List two examples of a Non-Renewable Energy Resource. 87. How does a turbine convert Kinetic Energy of its source into Electrical Energy? 88. How does a hydroelectric power plant transfer both Potential and Kinetic Energy into Electric Energy? 89. What type of Energy resource does not use a turbine to convert Mechanical Energy into Electrical Energy? 90. Why are Fossil Fuels considered to be non-renewable energy resources? 91. Why are Fossil Fuels not considered clean energy resources?

8 8 Answers: 1) Energy is the ability to do work. 2) An applied force and a displacement. 3) Work is the product of the force applied and the displacement of the object. 4) It would increase 5) Positive, the force applied is in the direction of the displacement 6) positive, the object is accelerating 7) 10 J, the air through air resistance 8) Mechanical and Non-Mechanical 9) The energy of an object due to its position or motion. 10) The energy of an object that is not due to its position or motion, but rather is energy at the atomic level. 11) It would remain constant 12) Air resistance is doing work against the man s displacement (negative work) and therefore causing the velocity to decrease. 13) No work is being done because the velocity is constant. 14) Negative work is being done because the velocity is decreasing. 15) 0 J 16) Potential and Kinetic energy 17) Electric and Nuclear energy 18) mass and velocity 19) it increases 20) Since the mouse has less mass than the elephant, it has to have a larger velocity in order to have the same kinetic energy. 21) 4 times larger 22) it is doubled 23) 360 J 24) 1,200 J 25) J 26) Joule (J) 27) when the object is not moving (velocity equals 0)

9 9 28) it decreases 29) it reduces by four times 30) it is cut in half 31) 162 J 32) 25 J 33) 7 times larger 34) mass, gravity, and weight 35) increases 36) decreases 37) decreases 38) cut in half 39) 49 J 40) 19,600 J 41) 110, 250 J 42) 19.6 J 43) 88.2 J 44) Joules (J) 45) when the height is zero 46) increases 47) doubled 48) 735,000 J 49) 22.8 J 50) 22.2 J 51) 47, 040 J 52) 3.7 J 53) The spring constant and the amount that the spring is stretched or compressed. 54) The elasticity of an object (how much an object stretches when an amount of force is applied). 55) Neither, both will have the same amount of potential energy. 56) The spring stretched 2X will have 4X more Elastic Potential Energy since the distance of stretch is squared.

10 10 57) 4X 58) 250 J 59) 31.3 J 60) 3.1 J 61) The length of a spring when it is not stretched 62) B spring constant is twice as large 63) 0 J 64) 100 J 65) 62.5 J 66) 4.7 J 67) A it is at the highest height 68) None there is no spring that is stretched or compressed 69) B it will be going the fastest because it is at the lowest point 70) All points have the same Total Energy 71) 3 the person is at the highest point 72) 1 the springs are stretched the most 73) 2 the person is going the fastest when he leaves the trampoline 74) All points have the same Total Energy 75) ho it has the highest height 76) None there is no spring that is stretched or compressed 77) at the point of contact between h0 and h1 because it is falling from the highest height 78) All points have the same Total Energy 79) A it is at the highest height 80) None there is no spring that is stretched or compressed 81) B it is at the lowest point and all GPE from A is converted into KE 82) All points have the same Total Energy 83) Energy resources that replenish themselves in a timely manner. 84) Energy resources that exist in limited supply and cannot be replenished in a timey manner 85) Wind. Solar, Water, Biomass, Geothermal 86)Fossil fuels and nuclear energy. 87) As the turbine moves it creates kinetic energy.

11 11 88) As the water falls from it converts from gravitational potential energy into kinetic energy. As the water flows by the turbine it moves the turbine doing work and creating electricity. 89) Solar Energy 90) Because the amount of time it takes to produce fossil fuels is much larger compared to the amount of time it takes to consume fossil fuels, 91) Because Carbon Dioxide is produced when it is burned.