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Name: _______________________ Date: ________ Period: ______ 7th Grade Science Mr. Vorstadt Chapter 14 Energy and Power A book on a shelf ledge has potential energy> It has stored energy that it took to lift it to the shelf. If the book is bumped and it falls, the potential energy changes to kinetic energy. The kinetic energy moves her to the other side of the swing where she slows down for an instant. She has potential energy at this point and then she swings back. If she doesn’t use any of her own energy to pump her legs, the swing will eventually come to a standstill. Why? _________________________________________________________ ______________________________________________________________ Describe the energy changes that occur for this boom-box radio. ______________________________________________________________ ______________________________________________________________ ______________________________________________________________ 1 Kinetic energy is measured in joules. A joule is the energy required to move an object one meter against the force of one Newton. 1. __________If a hammer has a mass of 2 kilograms and a velocity of 5 meters/second what is the kinetic energy of the hammer? 2. __________What would happen if we double the mass of the hammer but keep the velocity constant? 3. __________How would things be different if we kept the mass of the hammer at 2 kilograms but doubled its velocity? 4. __________If a rock has a mass of 20 kilograms is thrown at a velocity of 2 meters/second what is the kinetic energy of the rock? 5. __________What would happen if we doubled the mass of the rock by kept the velocity constant? 2 FORMS OF ENERGY Energy can never be destroyed: it is just changed from one form to another. When energy changes from one form to another some heat is given off that is useless to us, but no energy is destroyed. Directions: Think of energy changes that take place in your everyday life at home or school. Describe the energy conversions in the following way: Toaster ____________ Electrical energy changed to heat energy and radiant energy in order to toast the bread. _______________________________________________ _______________________________________________ _______________________________________________ ____________ _______________________________________________ _______________________________________________ _______________________________________________ ____________ _______________________________________________ _______________________________________________ _______________________________________________ Directions: Answer the following multiple choice questions _____ 1. Energy is the ability to do ________. a. work b. power c. acceleration d. speed _____ 2. The fuel used in a rocket is energy stored as __________ a. mechanical energy b. nuclear energy c. chemical energy d. electromagnetic _____ 3. Energy of motion is ___________ a. kinetic b. potential c. chemical d. solar _____ 4. A rubber band stretched between two fingers is an example of _______ a. kinetic energy b. potential energy c. chemical energy d. solar energy 3 _____5. To a scientist work is only accomplished when ... a. fuel is burned in an engine. b. an object is moved by a force. c. an object is lifted. d. something makes a sound. _____ 6. A force is defined as ... a. fuel for an engine. c. a push or a pull. b. an object that is moved a distance. d. none of these _____ 7. The energy of motion is called... a. force b. friction c. kinetic d. potential Directions: Below are a series of images showing Axle the Robot skiing down a hill. Decide how each image is an example of potential or kinetic energy. From the multiple choices, decide which is the best description of Axle’s position. _____ Picture one a. kinetic energy changing to potential b. potential energy c. kinetic energy d. potential energy changing to kinetic _____ Picture Two a. kinetic energy changing to potential b. potential energy c. kinetic energy d. potential energy changing to kinetic Look at the picture of a roller coaster. Identify the positions labeled with letters as either examples of points where the roller coaster cars have potential or kinetic energy. A. ___________________ 4 B. ___________________ C. __________________