11 Speed
Changing Speed and Direction
Typically an RN like Jolene will walk several miles over the course of a 12 hour shift on the MED floor. Her average speed (
) can be calculated as the distance covered divided by the time she worked. If she walks three miles, then her average speed would be:
(1) 
Jolene’s average speed is very different from her instantaneous speed at any one moment in time, which could be anything from zero to about 4.5 mph (she tries to avoid running in the hospital). Jolene’s instantaneous speed and direction of motion will change often as she starts, stops and turns corners. Typically we combine the speed and direction of motion into a single quantity known as the velocity, (
). When we care about the size and direction of a quantity we will call it a vector and make it bold just like do for forces when we are tracking their direction.
Reinforcement Exercises
average rate at which distance was traversed, equal to total distance traveled within a time interval, divided by the time interval
a quantity of speed with a defined direction, the change in speed per unit time, the slope of the position vs. time graph
a quantity with both magnitude (size) and direction
