Speed & Velocity

Definitions:

Speed: is a scalar quantity that refers to "how fast an object is moving."

Velocity: is a vector quantity that refers to "the rate at which an object changes its position."

Simple Definition:

Speed: how fast an object is moving.

Velocity: rate at which object changes position

General Information:

Speed can be thought of as the rate at which an object covers distance. A fast-moving object has a high speed and covers a relatively large distance in a short amount of time. Contrast this to a slow-moving object that has a low speed; it covers a relatively small amount of distance in the same amount of time. An object with no movement at all has a zero speed.

Velocity is a vector quantity. As such, velocity is direction aware. When evaluating the velocity of an object, one must keep track of direction. It would not be enough to say that an object has a velocity of 55 mi/hr. One must include direction information in order to fully describe the velocity of the object. For instance, you must describe an object's velocity as being 55 mi/hr, east. This is one of the essential differences between speed and velocity. Speed is a scalar quantity and does not keep track of direction; velocity is a vector quantity and is direction aware.

Practice Questions:

True or False:

1. Velocity is a vector quantity

2. An object with no movement has zero speed.

3. Velocity is direction aware

4. Speed is a vector quantity

Answers: 1.T, 2. T 3.T ,4.F