Speed and Velocity

Learning Objectives After completing this lesson you will be able to: Define the following terms: average speed, average velocity, constant speed, constant velocity, instantaneous speed, and instantaneous velocity. Distinguish among: speed and velocity; constant, average and instantaneous speed; constant, average and instantaneous velocity. Calculate: constant and average speed; constant and average velocity. Construct a position versus time graph or a displacement versus time graph of a moving object. Determine the displacement of an object on a velocity versus time graph or a position versus time graph. Interpret position versus time graphs or displacement versus time graphs to determine type of motion and position at a specific instant. Analyze position versus time graphs or displacement versus time graphs to determine constant velocity, average velocity and instantaneous velocity. Solve problems relating to speed and velocity. Use charts, tables and graphs to obtain numerical information. Estimate the velocity of various moving objects. Determine the slope of a graph and derive its correct units.

Key Concepts Scalar quantities consist of only a magnitude. Vector quantities consist of both a magnitude and direction and can be represented by a vector. Average speed (vav) is the total distance traveled divided by the change in time. Constant speed is when the object travels the same distance in equal periods of time. It is an example of uniform motion. Instantaneous speed is the speed of an object at a precise instant in time. Speed is a scalar quantity and its SI unit is m/s. Velocity is a vector quantity and therefore needs magnitude and direction. Its SI unit is m/s. Average velocity () is the total displacement of an object per unit time. Instantaneous velocity is the instantaneous speed in a specific direction. Constant velocity occurs when the object has the same displacement in equal periods of time. It is an example of uniform motion. Velocity is a vector quantity and therefore needs magnitude and direction. Its SI unit is m/s. Position-time graphs can be used to calculate velocity. Velocity-time graphs can be used to calculate displacement.