Distance, Time, Speed, and Velocity

Understanding Motion Motion is a change in position with respect to time. ( as you ride in a car, your position changes over time) In order to have a sense of motion you must have a reference point. A reference point is an object that is stationary, such as a tree or your house. Once the reference point is established, then your motion is defined in terms of position, direction, and speed.

Distance versus Displacement Distance is a measure of how far an object moves in relation to a reference point. If a truck travels 30 km from a loading dock to its next stop and then another 20km to the following stop, the total distance it travels is 50km.

Displacement Displacement is a measure of how far an oject moves in a certain direction. If a truck traveled 30 km east and then another 20km east, then the total displacement would be 50 km east. If the truck traveled 30 km east and then traveled back 20 km west, then the total displacement would be 10 km east.

Speed Speed is a measure of distance traveled per unit of time or how fast something is moving. Speed changes when something slows down or moves faster. You find the average speed of an object by determining the total distance traveled and dividing by the total amount of time. Speed = Distance / Time or S = D / T

Velocity The velocity of an object is a measure if its speed in a certain direction. The speed of an object may be 60 km / hr, its velocity may be 60 km / hr north, south, east, west, or any other direction. Velocity = Distance / Time or V = D / T You can find time by dividing Distance / Velocity or T = D / V You can find distance by multiplying velocity by time or D = VT