Transcription

1 Energy

2 What is Energy? Energy is the ability to do work. Any object that has energy has the ability to create force. Energy is one of the fundamental building blocks of our universe. Energy appears in different forms, such as motion and heat. Energy can travel in different ways, such as light, sound, or electricity. Energy is measured in joules, the same units as work, because energy is stored work. Any object with energy has the ability to do work.

3 Forms of Energy Mechanical - Mechanical energy is the energy possessed by an object due to its motion or its stored energy of position. Example: simple machines. Radiant - Radiant (meaning light) energy is also known as electromagnetic energy. Examples: visible light (light we see), x-rays, heat, and microwaves. Sun - Radiant heat from the sun keeps the Earth warm. We harness the radiant energy using solar power.

4 Forms of Energy (2) Electrical - Electrical energy is derived from other sources of energy such chemical energy from gas, heat energy from burning the gas, that heat energy is used to make steam which turns a turbine to produce mechanical energy, and the turbine turns an electrical generator to produce electrical energy.

5 Forms of Energy (3) Chemical - Chemical energy is the type of energy stored in molecules. Chemical reactions can either use or release chemical energy. Examples: the chemical energy in batteries is converted to electrical energy and your body uses chemical energy when it converts food into energy.

6 Forms of Energy (4) Nuclear Energy - Nuclear energy comes from splitting an atom (fission), or fusing two atoms together (fusion). Nuclear energy is used to generate or make electricity in power plants (fission). Nuclear energy is really the basic source for all other energy forms because it is how the sun and other stars make energy (fusion).

7 Forms of Energy (5) Thermal Energy Heat is a form of thermal energy.

8 Kinetic Energy Energy of a moving object is called kinetic energy.

9 Kinetic Energy (2) Kinetic energy depends on two things: mass and speed. Kinetic energy increases with speed. Consider a shopping cart with a certain speed. To make the cart move faster you need to apply a force to it. Applying a force means you have to do work. The higher the speed of the cart, the more energy it has because you have to do work to increase the speed. Kinetic energy increases with mass. If you give the same cart more mass, you have to push it with more force to reach the same speed. Increasing the mass increases the amount of work you have to do to get the cart moving, so it also increases the energy.

10 Calculating Kinetic Energy Kinetic energy is calculated using the following equation: KE (Joules) = ½ m (kg) x v 2 (m/s)

11 Potential Energy Potential energy is the stored energy resulting from the relative position of objects in a system. Potential energy is basically stored energy. Objects that have potential energy don t use their energy until they move. That s why it is called potential energy. Potential means that something is capable of becoming active.

12 Potential Energy (2) Consider a marble that is lifted off a table. Since Earth s gravity pulls the marble down, a force must be applied to lift it up. Applying a force over a distance requires doing work, which gets stored as the potential energy of the marble. Potential energy of this kind comes from the presence of gravity.

13 Calculating Potential Energy Potential energy is calculated using the following equation: PE = wh

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15 The Law of Conservation of Energy The law of conservation of energy states that energy can never be created or destroyed, just transformed from one form into another.

16 Energy Transformations Solar calculator (light to electrical) Windmill (mechanical to electrical) Glow stick (chemical to light) Firecracker (chemical to sound and light) Light bulb (electrical to thermal and light)

17 Example of Energy Transformation What happens if you throw a ball into the air? The ball has kinetic energy when it leaves your hand. As the ball gets higher it gains potential energy. So halfway up it has ½ kinetic energy and ½ potential energy. At the top of its flight the ball stops and has all potential energy and its speed is zero. At any moment in its flight the ball has exactly the same energy it had at the start. The energy is divided between kinetic and potential but the total energy is unchanged. Therefore, KE + PE = Total energy