# Glossary

acceleration - the rate at which velocity is changing. Acceleration is usually measured in meters per second per second (m/s2)

angular momentum - a quantity associated with how an object move around a reference point. It is often used to describe rotating objects. The angular momentum of an object is defined to be equal to its mass times its velocity about the point times its distance from that point.

axis of rotation - in a rotating object, the axis of rotation is the line about which the object is turning. The axis of rotation for a spinning record is its middle. The reference point for angular momentum is often chosen to be along the axis of rotation.

chemical energy - energy that is stored in your body and in molecules

conservation - the idea that the total amount of certain quantities in nature always stays the same. Energy, linear momentum, and angular momentum are examples of quantities that obey the law of conservation.

energy - a quantity associated with a system. Energy is often related to the motion of an object or the potential for motion. Kinetic energy, potential energy, chemical energy, and heat energy are examples of forms of energy.

force - an influence upon an object that causes motion or a change in motion

friction - a way that a form of energy, such as kinetic energy, is changed into another form, usually heat energy. Friction causes you to slow down when you are swinging. It also causes a spinning top to eventually fall over.

gravitational acceleration (g) - the constant describing the acceleration of any object falling toward the earth. Near the earth, gravitational acceleration is approximately equal to 9.8 meters per second per second (m/s2).

gravitational potential energy - a type of potential energy. Gravitational potential energy is associated in the interaction of an object with the earth. It is defined to be equal to the mass of the object times the gravitational acceleration times the distance of the object from the ground.

heat energy - a type of energy associated with temperature. Actual amounts of heat energy are difficult to measure.

kilogram (kg) - a unit or measurement for mass. A one-kilogram mass on a scale reads about 2.2 pounds.

kinetic energy - a type of energy describing an object's motion. Kinetic energy is defined to be equal to 1/2 times the object's mass times the square of the velocity of the object.

linear momentum - a quantity associated with the motion of an object along a straight path. The linear momentum of an object is defined to be equal to its mass times its velocity.

meter (m) - a unit for measurement for length. One meter is about equal to 3.3 feet or 1.1 yards.

potential energy - a type of energy having to do with how two or more objects are interacting. Potential energy is stored in the interaction of an object with another object. Gravitational potential energy is a type of potential energy.

quantity - a characteristic of a system that can be well described and possibly assigned values. Energy, linear momentum, and angular momentum are examples of quantities associated with all systems.

reference point - in angular momentum, the point in space around which the motion of an object is described. The angular momentum of an object is defined in relation to some point, the reference point. The velocity and radius of an object are measured from the reference point. The reference point is often chosen to be along the axis of rotation of a rotating object.

speed - how fast an object is moving

system - a group of objects

velocity - the speed of an object in a certain direction. Velocity is usually measured in meters per second (m/s)

Bang! Boing! Pop! Interactive Physics on the World Wide Web
Created for Thinkquest 96 by Josh Levine, Paulina Kuo, and Doug Brown