# FHSST Physics/Vectors/TO DO LIST

• Rewrite section on velocity to make clear the distinction between average and instantaneous rates of change (velocity and speed). The $\Delta$ 's in the equations imply we are calculating average quantities. Mention that we take the limit of a small time interval to give instantaneous quantities. Perhaps the example of a parabola with average gradient and gradient of tangent can be used as an illustration. Else defer until chapter on Graphs and Equations of Motion. Instantaneous velocity: reading on the speedometer in a direction tangent to the path. Instantaneous speed is magnitude of instantaneous velocity but average speed is not equal to magnitude of average velocity. Average speed and average velocity are the total distance and resultant displacement over the time interval related to that part of the path. The example of the circular track uses these definitions and is an important illustration of the differences. Instantaneous calculated at a certain instant in time while average is calculated over an interval.