Force
A push or pull that acts on an object
Inertia
The tendency of an object to resist a change in its state of motion
Friction
Opposes the motion of one object moving past another
Acceleration
A change in velocity
Speed
How fast an object's position is changing with time at any moment
Velocity
The speed and direction of a moving object
balanced forces
forces that cancel each other out when acting together on a single object
unbalanced forces
forces that do not cancel each other out when acting together on a single object
action
the force one object applies to a second as in Newton's third law of motion
reaction
the force with which an object responds to an action as in Newton's third law of motion
work
using force to move an object
simple machines
devices with few moving parts that make work easier to do
lever
consists of a rigid bar that rests on a pivot point
fulcrum
where the lever rests
effort arm
the part of the lever you apply an input effort force
resistance arm
produces an output force to lift the load
wheels and axle
a large-diameter wheel rotates in a circle around a small-diameter axle
pulley
a wheel with a groove in the rim
inclined plane
a flat, slanted surface that makes it easier to move heavy objects to higher levels
wedges
an inclined plane that is used as a tool for cutting or separating things
screws
an inclined plane wrapped in a spiral around a cylinder or cone