Unit Three Vocabulary Force and motion

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

Inertia The tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction until an outside force acts on the object.

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

Force A push or a pull exerted on an object in order to change the motion of the object; force has size and direction

The SI (International System of Units) unit for force (N) Newton The SI (International System of Units) unit for force (N)

The speed of an object in a particular direction Velocity The speed of an object in a particular direction

Acceleration The rate at which velocity changes over time; an object’s accelerates if its speed, direction, or both change.

The combination of the forces acting on an object Net Force The combination of the forces acting on an object

The total distance traveled by an object Displacement The total distance traveled by an object

Wheel and Axle A simple machine consisting of two circular objects of different sizes; the wheel is the larger of the two circular objects

Inclined Plane A simple machine that is a straight, slanted surface, which facilitates the rising of loads; a ramp

Lever A simple machine that consists of a bar that pivots at a fixed point called a fulcrum Fulcrum definition: the support, or point of rest.

Pulley A simple machine that consists of a wheel over which a rope, chain, or wire passes.

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

Wedge A simple machine that is made up of two inclined planes and that moves; often used for cutting

Work The transfer of energy to an object by using a force that causes the object to move in the direction of the force.