 # The Nature of Energy An unbalanced force must be applied to an object to change its motion. Work is the force over a distance. Energy is the ability to.

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The Nature of Energy An unbalanced force must be applied to an object to change its motion. Work is the force over a distance. Energy is the ability to do work. Energy is the ability to cause change.

Types of Energy There are 5 types of energy. Heat energy
Chemical energy Electrical energy Solar energy Nuclear energy

Kinetic Energy The energy of Example: run, walk, fall, or jump.
2 factors The size of the object (mass) Speed (faster = more kinetic energy)

Calculating Kinetic Energy
Equation: Kinetic Energy = ½ mass x Velocity² The SI unit for energy is the Joule (jewel). Because velocity is squared in the equation for kinetic energy, increasing the velocity of an object can produce a large change in its kinetic energy.

Heat Energy A form of Kinetic energy.
Heat is caused by the random motion and vibration of atoms and molecules in substances. Temperature is how we measure the amount of heat. Hotter the object, the faster the particles are moving.

Potential energy The energy that an object is able to store because of its position or condition. Gravity and size help items with potential energy. Potential energy is stored in the swing where it starts and stops, but converts to kinetic energy in-between.

Types of Potential Energy
1) Elastic Potential Energy Elastic Potential energy is energy stored by something that can be stretched or compressed, such as a rubber band or spring.

Types of Potential Energy
2) Chemical Potential Energy Energy that is stored in chemical bonds.

Types of Potential Energy
3) Gravitational Potential Energy (GPE) is energy stored by objects that are above Earth’s surface. The amount of gravitational potential energy depends on 3 things: A) mass B) Acceleration due to gravity (9.8 m/s²) C) height measured in meters

(GPE) Formula GPE = mass x 9.8 x height GPE is measured in Joules.
Problem: a .06-kg tennis ball starts to fall from a height of 2.9 meters. How much gravitational potential energy does the ball have at that height?

Solving the Problem Mass = .06 Acceleration = 9.8 Height = 2.9m
(GPE) M x A x H .06 x 9.8 x 2.9 = (GPE) = 1.7 Joules

The Transformation of Energy
Energy can change from one form to another. PE KE PE Chemical Energy Heat Energy Heat energy includes both exothermic and endothermic reactions.

Electrical Energy Electricity is formed by the movement of electrons.
Electrons are negative. Electricity can produce heat, light, sound, and magnetism. Electrical energy is transformed into another form of energy.

Chemical Energy A form of potential energy
The molecules store energy in their bonds formed by their shared electrons. When the bonds break, they release energy (kinetic) such as thermal energy.

Conversions Between Kinetic and Potential Energy
PE KE PE Mechanical Energy is the total amount of potential and kinetic energy in a system. Equation = Mechanical energy = Potential energy + kinetic energy Mechanical energy is energy due to the position and the motion of an object.

Energy Transformation
Most objects are sitting with a maximum potential energy or PE, but if the object starts to move, then the PE changes into Kinetic Energy. When the object has stopped moving, then the KE transforms back into the PE again. Example: An apple falling from an apple tree.

The Law of Conservation of Energy
The Law of Conservation of Energy states that energy cannot be created or destroyed. In a larger picture, this law means that the total amount of energy in the universe remains constant.

Where does energy go? Most energy is transformed into heat

Nuclear Energy When large nuclei split apart, they release free neutrons and energy. (nuclear fission) Joining the nuclei of smaller atoms together can also release stored nuclear energy. (Fusion) Example: The sun

Power Driven Machines Hydroelectric plant uses power from falling water to turn machines that make electricty. The Electricity is carried by wires to your home so they may convert from electricity to heat or light. Combustion Engines (automobiles) convert chemical energy (gas or fossil fuel) into heat energy and then into mechanical energy

Mechanical Waves Example: water or sound waves.
Longitudinal wave Mechanical Waves Sound waves Example: water or sound waves. The type of material that waves travel through is called a medium. (gas, liquid, or solid) Sounds travel faster in solids and liquids because the particles are closer together. Transverse wave

Electromagnetic Waves
Electromagnetic waves, (radio, light), do not require a medium to pass through. They can travel through a vacuum (space), and do not require particles of matter to carry their energy.

Electromagnetic Spectrum
Radio, microwave, infrared, visible light, ultraviolet, X-rays, and gamma rays make up the electromagnetic spectrum. All these waves travel at the same speed, but their frequencies and wavelengths differ. Radio waves have the lowest frequency/ longest wavelengths, whereas gamma rays have the highest frequencies and the shortest wavelengths.

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