Whiteboard Protocol Bell Work: What is the formula for acceleration? Objective: TLW how to calculate Kinetic and Potential energy. Classwork: beauregardchemistry.weebly.com/.../kinetic_and_potential_energy_ worksheet.docx Homework: Physics Book page 172; Practice D Exit ticket: What is the PE of a car with a mass of 50 kg and sitting on a hill that is 4 m tall? 7/20/2019 www.mrabynum.weebly.com
ENERGY The Ability to do Work
Energy can be defined as the ability to do work 7/20/2019 www.mrabynum.weebly.com
Energy There are many forms of energy Potential Energy Kinetic Energy Electrical Energy Mechanical Energy Gravitational Energy Chemical Energy 7/20/2019 www.mrabynum.weebly.com
POTENTIAL ENERGY Potential energy can be defined as energy at rest. Example: A pencil sitting on an edge of a desk A ball sitting still on the floor A rubber band stretched-out 7/20/2019 www.mrabynum.weebly.com
PE = MGH Potential Energy The formula for potential Energy is: 7/20/2019 www.mrabynum.weebly.com
Potential Energy Where: PE = Potential Energy M = Mass G = Gravitational Constant ( 9.8 m/s2) H = Height 7/20/2019 www.mrabynum.weebly.com
Potential Energy The formula for Potential Energy can be used to calculated the amount of energy used. Example: What is the Potential energy of a rubber ball that has a mass of 50 kg and is rolling down an incline that is 4 m high? 7/20/2019 www.mrabynum.weebly.com
Potential Energy The formulas for Potential Energy are as follows: PE = mgh ( Potential Energy) M = PE/gh ( Mass) H = PE/ mg (Height) 7/20/2019 www.mrabynum.weebly.com
Potential Energy The first step is to determine what has been given in the problem. PE = ? M = 50 kg G = 9.8 m/s2 H = 4 m 7/20/2019 www.mrabynum.weebly.com
Potential Energy = (50kg) (9.8 m/s) ( 4m) = 1962 J PE = MGH 7/20/2019 www.mrabynum.weebly.com
Potential Energy Example 2: Calculate the mass of a flying bird that is flying 8 m above the ground with a PE of 100 J. 7/20/2019 www.mrabynum.weebly.com
Potential Energy PE = 100 J H = 8 m G = 9.81 m/s M = ? What do we know? PE = 100 J H = 8 m G = 9.81 m/s M = ? 7/20/2019 www.mrabynum.weebly.com
M = PE/GH = 100 J / (9.81) (8 m) = 100 J / 78.48 = 1.27 kg Potential Energy M = PE/GH = 100 J / (9.81) (8 m) = 100 J / 78.48 = 1.27 kg 7/20/2019 www.mrabynum.weebly.com
Potential Energy Example 3: How high off the ground a bird is flying if its mass is 10 kg and it has a PE of 30 J? 7/20/2019 www.mrabynum.weebly.com
Potential Energy What do we know? PE = 30 J M = 10 kg H = ? G = 9.81 7/20/2019 www.mrabynum.weebly.com
Potential Energy H = PE / MG = 30 J/(10kg) (9.81 m/s) = 30 J / 98.1 = .31 m 7/20/2019 www.mrabynum.weebly.com
Summative Assessment Complete the following quiz found at this website: http://www.cstephenmurray.com/onlinequizes/physics/workandenergy/kineticvspotentialenergy.htm 7/20/2019 www.mrabynum.weebly.com