MOTION AND POSITION
Position is the location of an object in relation to a nearby object or place. The second object or place is called a reference point. A change in position is called motion.
Motion is any movement up, down, forward, or backward. To describe motion, you tell what direction an object moved from its earlier position as well as how fast it moved.
You know something is moving if its position changes against a background. The background is called the frame of reference.
(the background stays the same; the picture shows the same penguin in motion)
SPEED AND VELOCITY
One way to describe motion is to find speed or how fast or slow an object is moving. Speed tells you how the position of an object changes during a certain amount of time. You can measure time in hours (hr), minutes (min), or seconds (sec).
To find an object's speed, you divide how far it goes by the time it takes to get there.
Velocity is the speed of an object in a particular direction.
Example:
Speed: a car travels 55 miles per hour (mph)
Velocity: a car travels 55 mph, east.
FORCES
A force is any push or pull that causes an object to move, stop, or change direction.
Many forces act on you. Gravity is a force that pulls objects down to Earth.
Friction is a force that acts directly against the direction of motion. It is created by two objects moving against each other. Friction causes heat. (when you rub your hands together and feel the heat, this is friction!)
ENERGY
Energy is the ability to cause change in matter. EVERYTHING that moves has energy.
Kinetic energy is the energy of motion. Examples: moving water, wind, electricity.
Potential energy is the energy something has because of its position or condition. It is stored energy.