7 th Grade Science Name: Date: January 30, 2017 Unit: Packet: 4 Mechanical Homeroom: OBJECTIVES: By the end of class, students will be able to SWBAT define mechanical energy. SWBAT find an object s mechanical energy. DO NOW Agenda: 1. Do Now 5. Independent practice 2. Opening 6. Homework Overview 3. Notes 7. Closing 1. Guided Practice Homework: 4 A Devastating Storm Sandy was a Category 1 hurricane with winds near 90 miles per hour. Tropical storm-force winds extended almost 500 miles from its center. The storm first hit the Caribbean and was blamed for 65 deaths there before making its way north along the East Coast. A high-pressure ridge of air around Greenland blocked the hurricane from going out to sea as storms usually do. Instead, the storm shifted west toward land. SPENCER PLATT GETTY IMAGE A fire in Queens, New York destroyed over 50 homes during Hurricane Sandy. The eye, or center, of the hurricane hit land late Monday near the southern coast of New Jersey. It collided with a wintry storm from the west and cold air coming down from the Arctic. Brutal winds and close to a foot of rain were felt across hundreds of miles. Coastal areas, including parts of New York City and Long Island, experienced huge surges of seawater, made worse by high tides and a full moon. "This is the worst-case scenario," said Louis Uccellini, Environmental Prediction Chief for the National Oceanic and Atmospheric Administration. What is some evidence that Hurricane Sandy had energy? 1
Review: 1. Kinetic energy: The energy an object has due to its 2. Potential energy: that results from the shape or position of an object. This type of energy has the to do work. 3. Mechanical : The form of energy associated with the, and shape of an object. How Do You Find an Object s Mechanical? What do a falling basketball, a moving car, and a trophy on a shelf all have in common? They all have mechanical energy. The form of energy associated with the motion, position, or shape of an object is called mechanical energy. 2
Define Mechanical energy is the form of energy associated with the,, or of an object. Calculate At a certain point the kinetic energy of a falling apple is 5.2 J and its potential energy is 3.5 J. What is its mechanical energy? Infer If an object s mechanical energy is equal to its potential energy, how much kinetic energy does the object have? Got it I can find an object s mechanical energy by 3
Draw an arrow to represent the amount of Potential energy and Kinetic energy. 4
Mechanical Worksheet Potential = weight x height Kinetic = ½ x mass x speed 2 1. What are the two main forms of mechanical energy? 2. A car is lifted a certain distance in a service station and therefore has potential energy relative to the floor. If it were lifted twice as high, how much potential energy would it have? 3. Two cars are lifted to the same elevation in a service station. If one car is twice as massive as the other, how do their potential energies compare? 4. How many joules of potential energy does a 1-N book have when it is elevated 4 m? When it is elevated 8 m? 5. A moving car has kinetic energy. If the mass is doubled what happens to the amount of kinetic energy? If the speed is doubled what happens to the amount of kinetic energy? 6. Consider a ball thrown straight up in the air. At what position is its kinetic energy a maximum? Where is its gravitational potential energy a maximum? 7. What is the kinetic energy of a 2 kg snow ball thrown through the air at 5 m/s? 5
You Do: Show your work and units. No work. No units. 1. What are the formulas for the two main types of energy? 2. Who exerts more work: You moving a block 10 meters using 300 N or your friend taking 40 meters to move a weight of 40 N? Show all work. 3. Does the change in velocity and mass have the same effect on kinetic energy? Why or why not? 4. What is the amount of kinetic energy of truck with a mass of 2,000 kg going 10 m/s? 5. Which has more kinetic energy: a 100 kg person going 7 m/s or a 10 kg monkey going 15 m/s? 6. Calculate the gravitational potential energy of a 2,000 N elephant on an airplane that is 1,000 meters high. 7. What are the two main types of potential energy? Give an example of each. 6
8. If you wanted to increase the gravitational potential energy of an object, name 2 things that you could do? 9. Which has more gravitational potential energy: a 300 N cat at a height of 6 meters or a 50 N bird at a height of 50 meters? 10. Calculate the gravitational potential energy of a 20,000 kg plane at a height of 3,000 meters. 11. A ball is dropped from a cliff of 100 meters. a) When will the ball have the highest gravitational potential energy? b) When will the ball have the highest kinetic energy? c) At about what point in the fall will the kinetic energy of the ball equal to the gravitational potential energy? d) Does the Mechanical of the ball change during the drop? Why or why not? 12. A 0.5 kg ball has a height of 5 meters and it is traveling 1 m/s. What is the ball s mechanical energy? 7
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7 th Grade Science Name: Date: January 30, 2017 Unit: Lesson: 4 Mechanical Show your work and Show the units. No work. No Units. No Redo. Circle your answer Homeroom: /5 = % DNG? A B C D F 1. A 0.5 kg ball has a height of 5 meters and it is traveling 1 m/s. What is the ball s mechanical energy? 2. A person has a mass of 60 kg at a height of 3 m. What is the person s potential energy? 3. If you have more potential energy (either gravitational potential or elastic) will that be transferred to more or less kinetic energy? Why or why not? 4. Pretend that there is no air resistance. Determine the potential and kinetic energy for a 1 kg ball dropped at a height of 200 meters for 3 seconds. SHOW ALL WORK FOR CREDIT. (3 points) Time of Ball (seconds Height (m) Speed of Ball Gravitational Potential Kinetic Mechanical 0 200 Speed = GPE = KE = ME = 9
Time of Ball (seconds Height (m) Speed of Ball Gravitational Potential Kinetic Mechanical 2 180 Speed = GPE = KE= ME = Time of Ball (seconds Height (m) Speed of Ball Gravitational Potential Kinetic Mechanical 3 155 Speed = GPE = KE= ME = 5. If the kinetic energy of a falling object is 12 J and its potential energy is 35 J, what is its mechanical energy? 6. A rocket with mass of 5 kg is going straight up at 20 m/s at a height of 50 meters. What is the rockets potential energy? What is the rocket s kinetic energy? What is the rocket s mechanical energy? 10