Our physics expert picks his top-five equations, plus a scheme to supply US power needs with a bucket of baseballs. Thanks, ...

He defines what is meant by speed and how to calculate speed by applying the 'distance divided by time' equation ... misconception about the effect of a force on an object that is already moving.

Force diagrams and resultant forces Learn ... more about the difference between motion and speed and how to use the speed equation. Representing journeys Find out how to use distance-time graphs ...