Unit 4 - Forces and Matter

Position

the location of an object

Reference Point

A place or object used for comparison to determine if an object is in motion

Motion

An object's change in position relative to a reference point.

Speed

The distance an object travels per unit of time

X-axis

the horizontal line on a graph

Velocity

Speed in a given direction

Y-axis

the vertical line on a graph

Acceleration

rate of change of velocity

Force

A push or pull exerted on an object

Net Force

The sum of all forces acting on an object

Newton's First Law

an object at rest will stay at rest, an object that is in motion will stay in motion unless acted on by an unbalanced force.

inertia

The tendency of an object to resist a change in motion

Contact force

A force that is exerted only when two objects are touching.

Friction

A force that opposes motion between two surfaces that are in contact

Gravity

A force of attraction between objects that is due to their masses.

Balanced force

Equal forces acting on an object in opposite directions

Unbalanced force

Forces that cause a change in the motion of an object

Newton's Second Law

Force equals mass times acceleration

centripetal force

a force that acts on a body moving in a circular path and is directed toward the center around which the body is moving.

Newton's Third Law

For every action there is an equal and opposite reaction

Action/Reaction Pairs

two forces having equal strength in opposite directions

weight

A measure of the force of gravity on an object

orbit

The path an object follows as it moves around another object

Air resistance

force that opposes the motion of objects that move through the air

Work

A result of a force moving an object a certain distance.

Joule

unit of energy

Potential Energy

stored energy

Kinetic Energy

energy of motion

Mechanical Energy

the amount of work an object can do because of the object's kinetic and potential energies

Conservation of Energy

Energy cannot be created or destroyed; it may be transformed from one form into another, but the total amount of energy never changes

Thermal Energy

The total energy of motion in the particles of a substance

Chemical energy

potential energy stored in chemical bonds

Nuclear Energy

Energy stored in the nucleus of an atom

Electromagnetic Energy

A form of energy that travels through space as waves

Power

the rate at which work is done

Watt

unit of power

Machine

A device that makes work easier by changing a force

Mechanical Advantage

the number of times a machine increases a force exerted on it

Efficiency

The percentage of the input work that is converted to output work

Simple machine

A machine that does work with only one movement

Lever

a simple machine that consists of a bar that pivots at a fixed point called a fulcrum

Fulcrum

the pivot point of a lever

Wheel and Axle

a simple machine consisting of two circular objects of different sizes; the wheel is the larger of the two circular objects

Pulley

A type of lever that is a wheel with a groove in its rim, which is used to change the direction or multiply a force exerted by a rope or cable.

Inclined Plane

a flat, sloped surface

Wedge

A device that is thick at one end and tapers to a thin edge at the other end. It is an inclined plane that moves.

Screw

a simple machine that consists of an inclined plane wrapped around a cylinder

Compound Machine

a device that combines two or more simple machines