Science Explorer Motion, Forces, and Energy Chapter 1


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


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


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


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


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.


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.


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



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


A substance that can flow easily


The force that pulls objects towardEarth


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


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


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


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


a push or pull.


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


The tendency of an object to resist change in its motion


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


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