Forces and Motion

Speed

The distance an object travels per unit of time

Velocity

the speed of an object in a particular direction

Acceleration

The rate at which velocity changes

Weight

A measure of the force of gravity on an object

Mass

the amount of matter in an object

Newtons

The unit of measurement for force

Motion

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

frame of reference

a system of objects that are not moving with respect to one another

balanced forces

Equal forces acting on an object in opposite directions

unbalanced forces

Forces that produce a nonzero net force, which changes an object's motion

Newton's First Law

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

Newton's Second Law

Force = mass x acceleration

Newton's Third Law

For every action there is an equal and opposite reaction

Inertia

The tendency of an object to resist a change in motion

Friction

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

work

Force exerted on an object that causes it to move

Force

A push or a pull

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

Power

the rate at which work is done

Momentum

mass x velocity

simple machine

A machine that does work with only one movement

machine

A device that makes work easier

compund machine

a device that combines two or more simple machines

lever

Simple machine with a rigid bar that is free to move around a fixed point

Class 1 lever

A lever in which the fulcrum is between the load and the effort.

fulcrum

The fixed point around which a lever pivots

class 2 lever

A lever in which the load is between the fulcrum and the effort.

class 3 lever

A lever in which the effort is between the fulcrum and the load

Pulley

A simple machine that consists of a rope that fits into a groove in a wheel

single fixed pulley

this type of pulley changes only the direction of the force applied

single movable pulley

a pulley attached to the load being moved

compound pulley

a combination of several pulleys working together

incline plane

a sloping surface, such as a ramp, that reduces the amount of force required to do work

wedge

A device that is thick at one end and tapers to a thin edge at the other end.

wheel and axle

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

screw

A simple machine that is an inclined plane wrapped around a central cylinder to form a spiral

ramp

A slanted walk or roadway that connects a lower to a higher place.