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## Potential and Kinetic Energy (equals Mechanical Energy)

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**Energy**-A measure of the ability to change or move matter -Is measured in Joules (J)- hmm….just like work! -Whenever work is done energy is used**Potential Energy**• Energy stored in an object is called Potential Energy • There are Two Types of Potential Energy – • Elastic Potential Energy: Potential Energy Stored in a stretched object (i.e. rubber band, bungy cord, etc)**Potential Energy**• Gravitational Potential Energy: Potential energy an object has based on the force of gravity Depends on the mass (in kg) and height (in m) of an object Formula: Potential Energy = mass x gravity x height or PE=mgh**Potential Energy**What is the relationship between Work and Potential Energy? W = F x d PE = m x g x h F = weight = m x g**Potential Energy Practice**1. A 65 kg rock climber is climbing up a cliff. What is the climber’s gravitational potential energy 35 meters above the ground?**Potential Energy Practice**• 1. A 65 kg rock climber is climbing up a cliff. What is the climber’s gravitational potential energy 35 meters above the ground?**Potential Energy Practice**2. The potential energy of the climber is now 30,000 J. How high above the ground is the climber?**Kinetic Energy**• The amount of energy an object has because of its motion. • ANY object in motion • has kinetic energy • *including atoms! • The faster it moves, the greater its kinetic energy**Calculating Kinetic Energy**• Kinetic Energy = ½ mass x velocity2 or • KE= ½ mv2 • Notice that the velocity in the equation is squared. • Short video describing Kinetic Energy**Kinetic Energy**a small change in the velocity dramatically increases the kinetic energy a 2-kg ball rolling at 2 m/s = a 2-kg ball rolling at 4 m/s =**Kinetic Energy Practice**• Example: • 1. A 1500 kg car is traveling at 30 m/s. What is the kinetic energy? • 2. A boat has 10,000 J of kinetic energy. It is traveling at 15 m/s, what is the boat’s mass?**Conservation of Energy**• We add PE and KE to find Mechanical Energy • The total amount of energy in a system is CONSTANT!! • PE can become KE, and KE can become PE • This means that the SUM of both energies is always the same (KE + PE = ME).