D.S.Q. 1. What is kinetic energy? 2. What are some examples of kinetic energy?

Activity 1. Create a line of dominoes by standing each domino on its tall end. Space them close enough together so they will hit each other when they fall. 2. Your line may be straight or curved. 3. When the line is built, knock over the first domino with your finger and observe what happens.

Discussion 1. What did you observe when you knocked over the first domino in the chain? 2. How is this an example of kinetic energy? 3. How could you modify this experiment to stop the chain of falling dominoes before it reaches the end? 4. How could you modify the experiment to increase the kinetic energy in the middle of the chain?

Energy

Energy & Work Energy & work is measured in Joules Work is done when a force moves an object. For example: Putting a book into your backpack Energy is the ability to do work or cause change When energy is transferred, the object upon which the work is done gains energy Energy & work is measured in Joules

Power & Energy Power is the rate at which work is done Power = Energy Transferred Time

What are 2 types of energy? Potential and Kinetic Energy Kinetic Energy is energy in motion Potential Energy is stored energy

Kinetic Energy Kinetic energy of an object depends on both its speed and its mass What if you were hit with a tennis ball that was lightly tossed at you? Would it hurt? Now, what if you were hit with the same tennis ball but at a greater speed? The faster an object moves, the more kinetic energy it has

Kinetic Energy Continued Kinetic energy also increases as mass increases Which would have more kinetic energy, a tennis ball or a bowling ball?

Calculating Kinetic Energy Kinetic energy= Mass x Speed² 2 Example: Suppose a boy is pulling a 10 kg wagon at a speed of 1 m/s. What is the kinetic energy? 10 kg x 1 m/s² Answer: 5 Joules

Do the Math! Mrs. Kurtishi and her turtle are running. The turtle has a mass of 20 kg. Mrs. Kurtishi has a mass of 60 kg. 1. Suppose both the turtle and Mrs. Kurtishi run at a speed of 2 m/s. Calculate both of their kinetic energies. K.E of the turtle= K.E. of Mrs. Kurtishi =

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Potential Energy An object does NOT have to be moving to have energy Example: When you compress a spring by winding a toy, you transfer energy to it. However, the energy that is stored in it, might be used when it unwinds. Again, P.E. is stored energy, that results from the position or shape of an object

Solving for Potential Energy Formula is… P.E. (Joules) = Mass (kg) x Gravity (9.8 m/s²) x Height (m) OR you can solve P.E. by using the formula…. Weight (N) x Height (M) MAKE SURE TO CONVERT MASS INTO WEIGHT. INORDER TO DO THAT, WEIGHT = MASS X GRAVITY Now lets practice: A 3.0 kg scrub jay is squawking in an oak tree in Mrs. Fifield’s backyard. If the bird is on a branch located 20.0 m from the ground, how much potential energy does it have?

Gravitational Potential Energy (GPE) Potential Energy related to an object’s height is known as gravitational potential energy GPE is equal to the work done to lift to that height GPE (Joules) = Weight (N) x Height (Meters) Example: If a book weight 10 N and if the book is lifted 2 meters off the ground, what is the GPE?

Elastic Potential Energy (E.P.E) An object has a different type of potential energy due to its shape. E.P.E. is the energy associated with objects that can be compressed or stretched. Ex. Trampoline

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Forms of Energy Mechanical energy is the form of energy associated with the motion, position or shape of an object. Example: a falling basketball, moving car and trophy on a shelf

Calculating Mechanical Energy M.E. is a combination of both kinetic and potential energy The basketball in the next image has both p.e. and k.e. The higher the ball moves, the greater its p.e and the faster the ball moves, the greater the k.e. Mechanical Energy = P.E. + K.E.

Now you try! P.E. = 20 J K.E. = 2 J M.E. = P.E. = 12 J K.E. = 10 J

Mechanical Energy & Work An object with mechanical energy can do work with anther object. For example: A basketball does work on the net as it falls through the hoop. The net moves as a result. The more mechanical energy an object has, the more work it can do.

What are other forms of energy? Forms of energy associated with the particles of objects include nuclear energy, thermal energy, electrical energy, electromagnetic energy and chemical energy

Nuclear Energy Atoms are the small particles that make up objects The center of an atom is called the nucleus A type of potential energy called nuclear energy, is stored in the nucleus of an atom Nuclear energy is only released during a nuclear reaction Ex. When a nucleus splits or nuclear power plants which produce electricity

Thermal Energy The total kinetic and potential energy of particles in an object is called thermal energy Thermal energy is known as a type of kinetic energy The higher the temperature of an object, the more thermal energy the object has. Ex. Heating a pot of water. As the heat is applied to the water, the particles move faster and the temp. gets hotter

Electrical Energy Electrical energy is the energy of electric charges Ex. Getting shocked by metal Electrical energy can be either potential or kinetic energy

Electromagnetic Energy Also called radiant energy, is a form of energy that travels through space in waves Examples: Light Microwaves X-ray machines

Chemical energy Chemical energy is potential energy stored in chemical bonds Chemical energy is in the food we eat, the matched we use to light a candle and cells in out bodies

Energy Transformation & Conservation

How are different forms of energy related? What does flowing water have to do with electricity? In a hydroelectric power plant, the mechanical energy of moving water is transformed into electrical energy. ALL FORMS OF ENERGY CAN BE TRANSFORMED INTO OTHER FORMS OF ENERGY A change from one form of energy to another is called energy transformation.

Single & Multiple Transformations Some objects need either a single energy transformation, while others need multiple. Ex. 1: a toaster transforms electrical energy to thermal energy to toast your bread---that is a single transformation Ex. 2 : A car transforms multiple energies, such as electrical, thermal, and chemical

Kinetic & Potential Energy Transformation This is the most common transformation. Ex. When stretching a rubber band, you give it elastic potential energy. When you let it go, the rubber band flies across the room and has kinetic energy Ex. Pendulum

What is the law of conservation of energy? Looking back at the example of the pendulum, why doesn’t it keep going forever? What happens to the energy? According to the law of Conservation of Energy, when one form of energy is transformed to another, no energy is lost in the process. ENERGY CANNOT BE CREATED OR DESTROYED

What is the law of conservation of energy? As the pendulum swings, it encounters friction at the top of the string and from the air through which it moves. The kinetic energy then is transformed from mechanical energy to thermal energy