Force, Motion, and Energy
SOL 4.2 & Electricity SOL 4.3
HOW ARE OBJECTS LOCATION DESCRIBED?
The position of an object can be described by locating it relative to another
object or to the background. We use words like:
next to/beside
under
over
WHAT ARE MOTION AND SPEED?
Motion- is a measure of an object’s position over time
Speed-describes how fast an object is moving. Speed is a measure of
motion.
WHAT IS THE ABILITY TO DO WORK CALLED?
Energy. The ability to work is called energy.
HOW DOES ENERGY EXIST?
Energy exists in two states.
Kinetic energy-is the energy an
object has because it is moving.
Potential energy-is energy that
is stored or waiting to be used.
It gives the object the future
ability to do work.
A rolling bowling ball has kinetic
energy because it is moving.
A rock on a hill has potential
energy.
WHAT CAUSES AN OBJECT TO MOVE?
A force causes an object to move. A force is any push or pull that causes an
object to move.
Force
PUSH
PULL
Force can cause an object to move, stop, or change directions.
WHAT EFFECTS FORCE?
The greater the force, the greater the change in motion will be.
Tap
If you tap a golf ball with a club the
Strike
If you strike a golf ball with a club the
force will not be great, so the motion will
be small.
force will we great, so the motion will be
large.
WHY IS FRICTION A FORCE?
Friction is the resistance to motion created by two objects moving against each
other.
Friction is a force between surfaces that slows objects down or stops them
from moving.
The force that makes an object stop is called friction. Friction works against
motion. The surface of the object and what it rubs against it slows the object
and stops it from moving.
How much friction there is depends on the two objects involved.
If you push a cardboard box along a
sidewalk, there is a lot of fiction.
The smooth surface of the box is
hard to push along the rough surface
of the sidewalk.
You can easily ice skate across an icy
surface. Both the skate and the ice
have smooth surfaces, so they cause
less friction and motion is easier.
IF THERE IS NO FRICTION WILL AN OBJECT IN MOTION
EVER STOP MOVING?
Nope, it will continue moving forever. Kinda of neat huh?
IF AN OBJECT IS AT REST WILL IT MOVE WITHOUT A FORCE
APPLIED TO IT?
Nope, it will stay there forever or until a force acts upon it.
So remember, unless acted on by a force (like friction) an object in motion will
stay in motion and an object at rest will stay at rest until a force acts on it
(like a push or pull).
Electricity
SOL 4.3
HOW DOES ELECTRICITY FLOW?
In order for electricity to flow it must follow a complete path. The
pathway taken by an electric current is a circuit.
WHAT ARE THE TWO TYPES OF CIRCUITS?
Closed circuits- allow the movement of electrical energy. To be a closed
circuit there are no gaps or breaks in the path. A closed circuit is a circuit
through which electricity can flow.
Closed circuit
A circuit is closed because there are no gaps in the path that
electricity can flow.
Open circuits- can’t allow the movement of electrical energy because there
are gaps in the path.
Open Circuit
Open circuits prevent the flow of electrical energy
WHAT ARE TWO WAYS CIRCUITS CAN BE ARRANGED?
They can be either series circuits or parallel circuits.
series circuit
A series circuit only has one path for the electrical current to flow.
parallel circuit
In a parallel circuit there are two or more pathways for the electrical
current to flow.
WHAT ARE INSULATORS AND CONDUCTORS?
Insulators- are materials that do not allow electrons to flow through them.
Electrical energy does not go through them very well.
Insulators are used to keep electrical current from going where it isn’t wanted.
Some examples of insulators are:
rubber
wood
plastic
Conductors- are materials that allow electrons to flow through them.
Electrical energy moves through them easily.
metals
DO ALL MATERIALS CONDUCT ELECTRICITY EQUALLY?
No, among conducting materials, energy passes more or less easily depending on
its resistance.
WHAT IS AN ELECTRICAL CHARGE?
An Electrical charge is not something you can see, smell, or weigh.
All matter is made up of atoms. Inside atoms there are even tinier particles.
Some atoms have a negative electrical charge (-). Others atoms have a
positive electrical charge (+).
+Positive charge +
Opposite charges attract.
(pull toward each other)
-Negative charge-
Like charges repel each
other. (push away from each
other)
WHAT CAUSES STATIC ELECTRICITY?
Static electricity is caused by the build up of an electric charge on a material.
Have you ever walked across a carpet and gotten shocked? That was your feet
rubbing against the carpet. The static electricity was an electrical charge.
WHAT CAUSES LIGHTNING?
Lightning is a discharge of static electricity from a thundercloud.
Inside a cloud water and ice rub together. This separates the
negative and positive charges. Soon the build up is so great that a
large static shock, or lightning bolt occurs. (see pg. F73)
WHAT CAN ELECTRICAL ENERGY BE TRANSFORMED INTO?
Electrical energy can be transformed into heat, light, or mechanical energy.
Heat energy
Light energy
Mechanical energy