Physical Science Test 2 (Chapters 3-4)

Work

joule (J) 

• Zero distance, no work

• Displacement perpendicular to applied force, no work 

What is power?

The rate at which work is done. (Walking vs running upstairs). 

Units: watt and horsepower

How to Make Power?

work/time

Motion

an object changes its position with respect to time.

Position

 the location of an object at any given time.

Energy

the ability to do work

KE (Kinetic energy)

Energy associated with motion. Results from work or change in potential energy. (Speed squared)

PE (Potential energy)

Energy associated with position. Work and kinetic energy can change into potential energy.

Four Forces:

Strong Nuclear

Weak Nuclear

Electromagnetic force

Gravitational force

Strong Nuclear force

solar energy generation

Weak nuclear force

Carbon -14 converting to Nitrogen-14

electromagnetic force

 chemical bonds

Gravitational force

landslide

Energy Flow

based on the first two laws of thermodynamics 

Energy Transformation

the change of energy from one form to another.

Conservation of Energy

Energy is never created or destroyed.

Energy can be converted from one form to another, but the total energy remains constant.  

Conservation of Energy equation

Δ KE + Δ PE = 0

Energy Sources

nuclear energy, fossil energy and renewable sources like wind, solar, geothermal and hydropower.

Petroleum

a complex mixture of hydrocarbons that occur on Earth in liquid, gaseous, or solid form

Coal

a sedimentary deposit composed predominantly of carbon that is readily combustible.

Hydroelectric

a form of energy that harnesses the power of water in motion—such as water flowing over a waterfall—to generate electricity.

Solar

any type of energy generated by the sun

Wind geothermal

 a renewable energy source because heat is continuously produced inside the earth.

Nuclear

a form of energy released from the nucleus, the core of atoms, made up of protons and neutrons.

Hydrogen

an energy carrier that can be used to store, move, and deliver energy produced from other sources.

Biofuels

offer a solution to one of the challenges of solar, wind, and other alternative energy sources.

Mechanical energy

Kinetic plus potential energy

Electrical energy

Charges, currents, etc.

Chemical energy

Energy involved in chemical reactions

Radiant energy

Electromagnetic energy; Visible light = small part of full spectrum 

Nuclear energy

 Energy involving the nucleus and nuclear reactions

Simple Machines

Work in equals work out

Force multiplied by ratio of distance

Simple machine examples

• Inclined plane

• Wedge

• Screw

• Lever 

• Wheel and axle

• Pulley

1st Law of Thermodynamics

Energy cannot be created or destroyed. 

2nd Law of Thermodynamics

For a spontaneous process, the entropy of the universe increases.

3rd Law of Thermodynamics

A perfect crystal at zero Kelvin has zero entropy.

Entropy

Measure of disorder

Phase changes

 Melting

Boiling

Evaporation

Condensation

Melting

The process of a solid becoming a liquid (fusion) 

Boiling

 Heat going into a substance changes it from a solid to a liquid or a liquid to a gas.

Evaporation

the process of changing from a liquid to a vapor

Condensation

a substance is changed from the gaseous to the liquid state of matter

Kinetic molecular theory

Gasses are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion.

Phases of matter

 solid, liquid, and gas

Solid

 a state of matter that retains its shape and density when not confined.

Liquid

conforms to the shape of its container but retains a nearly constant volume independent of pressure

Gas

a substance that does not have a definite volume (also called a fixed volume) or a definite shape.

Fahrenheit

 scale based on 32° for the freezing point of water and 212° for the boiling point of water, the interval between the two being divided into 180 equal parts.

Celcius

a temperature scale based on 0o for the freezing point of water and 100o for the boiling point of water.

Kelvin Heat

the SI unit of thermodynamic temperature

Units

used to measure a physical quantity, such as mass or length

Specific Heat

the quantity of heat required to raise the temperature of one gram of a substance by one Celsius degree.

Latent Heat

 the heat or energy that is absorbed or released during a phase change of a substance.

Conduction

 the transfer of thermal energy between two objects by direct contact

Conduction example

ie. a metal cooking pot sitting in an air-conditioned house feels cold when you touch it.

Convection

motion in a gas or liquid in which the warmer portions rise and the colder portions sink

Convection example

ie. Hot air rising above a fire.

Radiation

a process where heat waves are emitted that may be absorbed, reflected, or transmitted through a colder body.

Radiation example

ie. The heating of the Earth by the Sun