#### Science Explorer Motion, Forces, and Energy Chapter 1

Motion

An object is in _____ when its distance from another object is changing.

Reference Point

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

International System of Units (SI)

A system of measurement used all over the world. The system is based on the number ten, to make calculations relatively easy. It is used to measure both lengths and quantities

Meter

The Basic SI unit of length. It consists of 100 cm, 1000 mm, 10 dm, and is 0.001 m of a kilometer.

Centimeter

A smaller unit of measurement in the metric system. It consists of 10 mm and is 0.01 m of a meter.

Kilometer

A unit of measurement in the SI that consists of 1000 meters.

Speed

The distance the object travels per unit of time. Modeled by the equation S=D/T

Constant Speed

An object with a speed that does not change.

Average Speed

The average distance an object travels over a certain period of time.

Velocity

Speed in a given direction. It is the same calculation as speed, but direction is included. Weather forcasters and air traffic controllers use velocity to determine wind speeds and plane speeds.

Graphing Motion

Time is on the x axis, distance is on the y axis.

Acceleration

The rate at which velocity changes. In science, ________ refers to increasing speed, decreasing speed, or changing direction.

Acceleration Equation

Final Velocity-Initial Velocity/Time

Acceleration Units

meters/second/second

sliding

When solid surfaces slide over each other, the kind of friction that occurs is ______________ friction.

fluid

A substance that can flow easily

gravity

The force that pulls objects towardEarth

free

When the only force acting on a falling object is gravity, the object is said to be ________ in fall.

air

Objects falling through air experience a type of fluid friction called ____________ resistance.

momentum

The _________ of an object is the product of its mass and velocity.

pressure

The force exerted on a surface divided by the area over which the force isexerted

Force

a push or pull.

Net

The overall force on an object after allforces are added together is called theforce.

inertia

The tendency of an object to resist change in its motion

newton

One _________ equals the force required to accelerate 1 kilogram of mass at 1 meter per second per second.

friction

The force that one surface exerts on another when the two rub against each other