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Policastro/Finizio Contemporary Physical Science Period 4 Quiz Date: 1/12/05 Pendulum Problems, Work Problems, and Section 15.1 Study Guide Formulas 1. Potential Energy = mass gravity height *Remember Gravity always equals 9.8 *Unit for Potential Energy is Joules 2. Kinetic Energy = 1 mass velocity 2 2 *unit for Kinetic Energy is the Joule 3. Force = weight ( Kg ) 10 *unit for Force is the Newton 4. Work = force dis tan ce *unit for work is the Joule Section I: Kinetic/Potential Energy Problems Sample Problem #1 Calculate the kinetic energy of a 1kg toy car traveling at a constant velocity of 2 m/s. Step #1: Determine what Formula to use. This question asks us to calculate Kinetic Energy. Therefore we will use the following formula. 1 mass velocity 2 2 *In order to calculate the Kinetic Energy, you must plug your numbers into the formula. Mass = 1kg Velocity = 2 m/s KineticEnergy 1 (1)(2) 2 Kinetic Energy = 1 Joule Sample Problem #2 Find the Velocity of a Pendulum using the given data. Mass: 3 Kg Height: 1 meter Step #1: Find the Potential Energy of the Pendulum. In order to do this use the following formula. P.E. = (m)(g)(h) Potential Energy = (3)(9.8)(1) Potential Energy = 29.4 Joules Step #2: Since we are looking for Velocity we can use the Kinetic Energy formula. Place the Potential Energy you found in for Kinetic Energy. Set it up as follows 1 29.4 m v 2 2 29.4 1 3 v2 2 Step #3: Solve this equation for V. In order to do this you must isolate the V 29.4 1 3 v2 2 29.4 3 2 3 2 v 2 3 2 Divide both sides by 19.6 v 2 19.6 v2 4.43 v Final Answer 3 2 Section II. Work Problems What is the work done by a weight lifter who lifts a 1600-newton barbell over his head? Assume that the barbell is lifted to a height of 2.0 meters. Formula Needed: Work = force dis tan ce In this problem: Force = 1600 N Distance = 2.0 m Therefore the Equation you must set-up is: Work = 1600 2.0 Work = 3200 Joules Section III: Section 15.1 Key Terms Energy Kinetic Energy Potential Energy Gravitational Potential Energy Elastic Potential Energy Mechanical Energy Thermal Energy Chemical Energy Electrical Energy Electromagnetic Energy Nuclear Energy Key Points Energy is the ability to do work. When work is done on an object, energy is transferred to that object. The energy of motion is called Kinetic Energy. Potential Energy is energy that is stored as a result of position or shape An objects potential energy depends on its mass, its height, and the acceleration due to gravity. The potential energy of an object that is stretched or compressed is known as Elastic Potential Energy. The energy associated with motion and position of everyday objects is mechanical energy. The total potential and kinetic energy of all the microscopic particles in an object make up its thermal energy. Chemical Energy is the energy stored in chemical bonds. Electrical Energy is the energy associated with electric charges Electromagnetic Energy is a form of energy that travels through space in the form of waves The energy stored in atomic nuclei is known as Nuclear Energy. The unit of energy is the Joule. Practice Problems 1. Calculate the kinetic energy of a 0.25-kg toy car traveling at a constant velocity of 2 m/s. 2. Calculate the potential energy of a 3-kg pendulum that is held 2 m in the air. 3. Calculate the Kinetic energy of a 1.5 kg remote control car that is traveling at a constant velocity of 5 m/s. 4. Calculate the velocity of a pendulum using the following data. a. Mass = 2 kg b. Height = 2 meters 5. Calculate the velocity of a pendulum using the following data. a. Mass = 4 kg b. Height = 5 meters 6. John has an object suspended in the air. It has a mass of 50 kilograms and is 50 meters above the ground. How much work would the object do if it was dropped? 7. Calculate the work done by a weight lifter who lifts 100 kilograms 2 meters off the ground. *In addition to this study guide be sure to study all class notes and assignments. This includes the reading and questions that you did in Section 15.1 of your Textbook. *