MotionChapter 1, Section 1

Describing and Measuring Motion

Describing Motion

ONot always easy to describe if an object is moving

O“An object is in motion if its distance from another object is changing.” (p7)

OReference Point – a place or object used for comparison to determine if something is in motion. (p7)OUse objects like trees or

buildings

OThe answer to the question “is it moving?” depends upon the reference point chosen.OEx. A chair vs. the sun (p.8)

OUse measurement to be more specific when describing motion.

OInternational System of Units (SI) – system of measurement used by scientists.

OUnit of measurement used for length is meters (m)OMay also be in centimeters

(cm), millimeters (mm), etc.

Calculating SpeedO You can calculate speed if you know

both the distance and object traveled and how long it took to reach its destination.

O Speed = Distance / TimeO If distance is measured in meters

and time is measured in seconds, your answer would be labeled m/s (meters per second).

OMost objects to not move at a continuous speed. It changes as the object moves (may speed up or slow down)

OAverage Speed – total distance traveled divided by the total time.

O Instantaneous Speed – the rate at which an object is moving at a specific time.

Describing VelocityO To fully describe the motion of an

object you also need to know the direction it is traveling.

O Velocity – speed in a given directionO Ex. 25 mph westO Important for air traffic controllers to

know the speed and direction of planes

O Important for pilots and stunt pilots to be able to keep control of the airplane

Graphing Motion

OTo show motion in a graph, create a line graph.

OTime is on the x-axisODistance is on the y-axis