Science ch 9 (6th grade)

potential energy

energy that is stored in an object due to its position or condition of an object; stored energy

kinetic energy

energy due to motion

mechanical energy

Kinetic or potential energy associated with the motion or position of an object

Motion

change in an object's position

reference point

the starting point you choose to describe the location, or position, of an object

distance

The amount of space traveled from where an object starts to where it is at any given moment

Speed

The distance an object travels per unit of time; Distance divided by time equals speed, measured in length units per time units

instantaneous speed

the speed of an object at one instant of time; speedometer on cars

Formula for Distance

distance = speed x time

velocity

the speed of an object in a particular direction; refers to speed and direction

Acceleration

rate of change of velocity; the faster the velocity changes, the greater the acceleration

force

A push or pull is exerted on an object

friction

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

momentum

The product of an object's mass and velocity

Galileo Galilei (1564-1642)

Italian astronomer and mathematician. Developed his laws of motion, establishing the study of physics- a moving object does not come to rest unless an outside force acts on the object

Issac Newton (1642-1727)

Continuing Galilei's study of how and why things move, he formulated the 3 laws of motion

First law of motion

The velocity of an object does not change unless an external force acts upon the object; an object with zero velocity tends to stay at rest

inertia

The tendency of an object to resist a change in motion

gravity

A force that pulls objects toward each other

weight of an object

The weight of an object is the force of gravity on the object and may be defined as the mass times the acceleration of gravity, a measure of force

Second law of motion

States that force is equal to an object's mass times the acceleration of the object; the greater the mass, the greater the force needed to move it.

Third law of motion

For every action there is an equal and opposite reaction

Work

Defined as a force acting on something as it moves a certain distance; force times distance = work

newtons (N)

The unit of measurement for force

Joule (J)

The unit used to measure work

machine

A device that makes work easier

effort force

The force applied to a simple machine

resistance force

resistance: the force that works against the effort

lever

A simple machine that consists of a rigid bar that pivots about a fixed point.

fulcrum

fixed point on a lever; the spot where the bar turns or pivots

First-class levers

The fulcrum is between the effort and the load; seesaws and crowbars

Second-class lever

The resistance between the effort and the fulcrum, a door and a wheelbarrow; most anything that has a hinge

Third-class lever

The effort is between the resistance and the fulcrum: a broom and a fishing pole

pulley

A simple machine that consists of a grooved wheel with a rope or cable wrapped around it.

fixed pulley

attached to something that doesn't move

moveable pulley

moves with the load or resistance

block and tackle pulley

a pulley system made up of fixed and movable pulleys

Mechanical advantage

The decrease in effort that is needed to move an object

wheel and axle

Consists of a wheel and a rod, or axle, running through the wheel

Turbine

A device with blades that can be turned by water, wind, steam, or exhaust gas from combustion that turns a generator in an electricity-producing plant

gear

A type of wheel and axle that has toothlike projections around the wheel.

Inclined plane

a flat, sloped surface, such as a ramp

wedge

Two inclined planes placed back-to-back and used to split or lift objects

screw

An inclined plane wrapped around a cylinder or cone; ridges in the screw are called threads

compound machine

a machine made of more than one simple machine; scissors