Chapter 5

Energy What is Energy? Kinetic Energy: Energy in the form of motion Running, spinning wheels, etc. Potential Energy: Stored energy

Work Definition: The transfer of energy through motion. A force is exerted over a distance. Equation: W = F x d

Practice Problem: A dancer lifts a 400N ballerina overhead a distance of 1.4 m. How much work has he done? W = F x d W = 400N x 1.4m W = 560 N  m W = 560 J

Practice Problem: A game show contestant won a prize by pushing a bowling ball 20m using his nose. The amount of work done was 1470J. How much force did the person exert on the ball? F = W / d F = 1470J / 20m F = 73.5 N

Conservation of Energy Pendulums

Mechanical Energy The total amount of kinetic and potential energy.

Law of Conservation of Energy Energy can change form, but it can not be created or destroyed.

Energy and the Human Body Movement The movement of your body is the conversion of your bodies potential energy into kinetic energy. The food you eat is your chemical potential energy. Calorie: The unit used to measure how much energy we get from specific foods.

Temperature and Heat The measure of the average kinetic energy of the particles in a sample of matter. The measure of how hot and cold an object is compared to a reference point. Reference points could be on a temperature scale, like the freezing and boiling points of water

Thermal Energy: Thermal energy is the total potential and kinetic energy of all the particles in an object. Thermal energy depends on the mass, temperature, and phase (solid, liquid, or gas) of an object.

Heat: Heat is the transfer of thermal energy from one object to another because of a temperature difference. Heat always flows from hot objects to cold objects.

Comparing Temperature Scale There are three different temperature scales that are commonly used. Fahrenheit (F) Celsius (C) Kelvin (K)

Common Temperatures Fahrenheit Celsius Kelvin Water Boils 212 100 373 Human Body 98.6 37 310 Average Room 68 20 293 Water Freezes 32 273

Measuring Thermal Energy Specific Heat: The amount of heat needed to raise the temperature of one gram of material by one degree Celsius. The lower the material’s specific heat, the more its temperature rises when a given amount of energy is absorbed by a given mass.

Specific Heat Every material that exists has a different Specific Heat.

Specific Heat Equation: Q = m x c x T Q= Change in Thermal Energy M = mass C = Specific Heat T = (final temp – initial temp)

Practice Problem 1. A 45 kg brass sculpture gains 180,480 J of thermal energy as its temperature increased from 28-48 C. What is the approximate specific heat of brass? Q = c m x T

Chapter 6

Using Thermal Energy Conduction: The transfer of energy through matter by DIRECT contact. Convection: The transfer of energy by BULK MOVEMENT of matter Radiation: The transfer of energy in the form of waves.

Conduction

Convection

Radiation

Thermal Energy Flow Conductors: Any material that allows heat to move easily. Insulators: Any material that does not allow heat to move easily. Insulation Ratings R-value: A scale that compares the insulation ability of different materials.

Chapter 7 Machines…..

Machines: Making Work Easier by…. Lifting our cars (jacks) Helping us climb (stairs) Moving us (wheels and axles)

What are Machines? A device that makes work easier by changing the force. They change the size of the force needed, the direction of the force or the distance over which a force acts.

Advantages of Machines Can increase the amount of force on an object. Lug nut Can increase the distance that the force must work within Pulley Can change the direction of the force Oar

Simple Machines Levers: A rigid bar that moves around a fixed point called a fulcrum. When you put force into a lever it will produce a different amount of output force.

Levers First Class Lever: The fulcrum is located between the input force and the output force.

Levers Second Class: The output force is located between the input force and fulcrum.

Levers Third Class: The input force is located between the fulcrum and the output force.

Simple Machines - Pulley Pulleys are simple machines made from a rope that fits into the groove of a wheel. Types of pulleys Fixed Movable Pulley System

Simple Machines: Wheel and Axle A ‘Wheel and Axle’ is a simple machine that consists of two disks (or cylinders), each one with a different radius.

Simple Machines: Inclined Plane An Inclined Plane is a slanted surface that can move an object at a different elevation.

Simple Machines: Screw A Screw is an inclined plane wrapped around a cylinder. Screws with threads that are closer together have a greater ideal mechanical advantage.

Simple Machines: Wedge A Wedge is a V-shaped object whose sides are two inclined planes sloped towards each other.

Using Machines A Compound Machine is a combination of two or more simple machines that operate together. Car, washing machine etc.

Power Definition: Power is the rate of doing work. Equation: To increase power you whether increase the work done in a given time, or do the amount of work in less time. Equation: Power = work / time Remember!!! Work = Force x distance

Power Practice Problems: A figure skater lifts his partner, who weighs 450N, 1.0m in 3.0s. How much power is required? Power = work / time Power = (Force x Distance) / time Power = (450N x 1.0 m) / 3.0 s Power = 450 J / 3 sec Power = 150 Joss or…… 150 W (Watts)

Watts Watt is the SI unit for power. It represents the amount of Joules per second For example, a 40 Watt light bulb requires 40J of energy for every second that it is lit.

Chapter 21 Electricity

Static Electricity: The property that causes subatomic particles such as protons and electrons to repel each other. There are two types of electrical charge, Positive and Negative. Positive charges from protons Negative charges from electrons.

Static Electricity: Electric Fields The effect an electric charge has on other charges in the space around it. The charge of static electricity can be transferred by friction, contact or induction.

Friction: Rubbing, build up of charges Contact: Touching something directly Induction: Transfer of charge without direct contact.

Electric Conductors and Insulators Conductor: A material through which a charge can easily flow Insulator: A material through which a charge can not easily flow.

Electric Current Flowing Electrons: Electrons that move or flow in one direction produces an electric current. Potential Difference: The difference in electrical energy between two places in an electric field. Current: Direct Current (DC): A current where the charge only flows in one direction. Alternating Current (AC): A flow of electric charge that regularly changes its direction.

Battery Dry cell: LEAVE BLANK Wet cell: LEAVE BLANK

Electrical Circuits Symbols (page 609) Series: Has only one path that the electricity can flow Christmas lights Parallel: Has two or more paths for the flow to travel Household circuitry

Chapter 22 Magnetism

Magnets Magnetism: The force a magnet exerts on another magnet, can attract or repel. Magnetic Field: Is strongest near a magnet’s poles will either attract or repel another magnet that enters the field.

Poles / Magnetic domains The parts of the magnet that are the strongest North and South Opposites attract