Physics Notes 2012-2013

Simple Machines

1. pulley – used to lift heavy objects or to lift objects

to certain heights. An example of a pulley is a

clothesline

2. wheel and axle – used for transportation or people or things

An example of a wheel and axle is a skateboard,

wheel barrow

3. incline plane (ramp) - is used to raise

objects. An example is a wheel chair ramp,

or a boat ramp

4. lever and fulcrum – used to lift heavy items or

to get items airborne. An example is your

arm, shovel, ax

5. wedge – used to separate. For example a door

stop

6. screw – used to hold objects together or to create a

hole

7. gear – teeth that fit together and move things

An example is the inside of a watch, bike chain

Inventions & Discoveries

Inventions: something created or made to make life easier

-automobile

-telescope

Discoveries: something that already exists that you find a use for

-gold

-electricity

Motion, Energy & Simple Machine

People could not live without MOTION – planets in orbit, waves, loop roller coasters.

motion – a continuous change of position. Motion is only seen when

compared to a stationary (still) object. You have to see something

that is not moving in order to tell that something else is moving.

-the earth rotates at a rate of 1,000 miles per hour.

-gravity works against motion

-friction works against motion and produces heat

How Can you describe Motion??

Distance, measured in Metric meters

Speed can be calculated with a formula

Speed = distance

Time

Velocity - speed and direction

Acceleration - The rate at which velocity changes

force – a push or pull one body exerts on another.

What Affects Motion?

1. friction- A force that resists motion between objects that are touching. The more friction there is, the more heat there is.

Scientist Galileo (1564-1642)

Experiments concerning motion. He discovered that no force was needed to keep an object in motion. Instead, objects slow down or stop because the force of friction is acting on them.

2. gravity – The force of attraction between objects. “What goes up MUST come down.” The earth’s gravity pulls all objects toward the center.

Two Factors that Affect Gravity

1. mass – the larger the object, the greater the gravitational pull.

2. distance – closer objects are, the greater the gravitational pull.

Gravity & Balance

Center of Gravity – everything has a center of gravity. Can you balance a ruler on your finger? The place where the ruler balances is the center of gravity.

In science, a law is a statement that can be proven. The scientist Isaac Newton developed three laws of motion in the 1660s. These laws of motion are about events or relationships that exist in nature.

Newton’s Three Laws of Motion

1. An object in motion tends to stay in motion. If it is at rest, it

tends to stay at rest, unless a force causes it to change. This is

called inertia. (/in/-/er/-/sha/)

Example:while in a car, quick starts make you go backward

quick stops make you go forward

quick curves make you go the opposite way

2. An object will begin to move in the direction a force is applied to

it. Example: pushing a wagon or pulling a rope

The greater the mass of an object, the more force is needed to move the object. Therefore, to move a large mass at the same rate as a small mass, you have to apply more force to the larger mass.

3. For every action, there is an equal and opposite reaction.

Example: When walking your foot exerts a backward force and the

ground exerts an equal force pushing you forward. On ice, the

forces between your foot and the ground are unequal, causing you

to fall.

Energy

energy – the ability to do work or cause change

work – is done when something moves

Two types of energy:

1. potential – stored energy to be used later, for example a stationary

rock.

2. kinetic – energy present when it is moving; energy that is moving,

it is in use. For example, a rock rolling down a hill.

Kinds of Energy

1. chemical – this energy results from the forces that hold atoms and

molecules together, for example dynamite or gasoline.

2. electrical – energy that results from the movement (transfer) of

electrons, usually through a conductor.

3. heat – random movement of particles. The faster the particles

move, the more heat is made. Heat is a form of kinetic energy.

4. light – the energy from natural things (the sun, stars and fires) and

from man-made objects (light bulbs). Light is the most plentiful

source.

5. magnetic – this energy is naturally present in iron, nickel and

cobalt. The Earth acts like a magnet, especially at the poles.

Electromagnetics combine magnets with electricity. They are

magnets that can be turned on and off, like doorbells.

6. mechanical – this energy can be potential energy when it is not

moving. However, it is usually thought of as the kinetic energy of

moving objects. This energy is released by human muscles moving

(running, jumping, etc.) as well as by machines (trains, cars and

anything with gears.)

7. nuclear – is also called atomic energy. It is a very powerful form

of potential energy. Very large amounts of kinetic energy can be

produced by splitting atoms (fission) or by joining an atom with

another atom (fusion).

8. sound – the energy produced when matter vibrates, for example

vocal chords, horns, musical instruments.

Energy Transfer

Energy transformation – when one form of energy changes into another form of energy.

Fact – potential and kinetic energy can change from one form into the other.

For example, a match (chemical energy) turns into light and heat energy.

Law of Conservation of Energy

Energy cannot be created or destroyed! It can only be transferred from one object to another. However, the amount of total energy always remains the same.

Electricity

atoms – made up of protons, electrons and neutrons

protons – the positively charged particles in the nucleus of the

atom

electrons – the negatively charged particles that move around the

nucleus

neutron – the particle that has no charge, they are neutral

How Electricity Works

An atom has no charge because the protons and electrons balance each other out. However, electrons have less mass than protons so they move more quickly. The outer most electrons can be easily pulled away. When an atom loses electrons, it becomes a positively charged ion. Such charged particles are the basis of electricity.

Electricity and Magnetism

Static electricity – electric charges are transferred from one object to another, it is movement of electrons.

  • If there are more electrons –it is a negative charge
  • If there are more protons – it is a positive charge

electric currents – movement of electrons in a material.

closed circuit – electrons leave the (-) side of the battery, flow through wires and bulbs and return to the (+) side of the battery where electrons are missing.

conductor – a material that allows electrons to flow through it.

insulator – a material that does not allow electrons to flow through it.

Circuits

current – the flow of energy through a circuit

voltage – the potential energy in a battery that can be used to send a current through a circuit (measured in volts)

series circuit – one pathway for the flow of electrons

When one bulb goes out, the next bulb won’t light. Each bulb is part of one loop.

parallel series- branches into separate pathways for the flow of electrons.

Each bulb has its own independent loop. Electricity can flow into each loop separately, so if one bulb burns out, the other stays lit.

resistance- how hard it is for energy in a battery that can be used to send a current through a circuit. (measured in volts)

current- the flow of energy through a circuit (measured in amps)

watt- measure of the amount of electricity