Position and Displacement
Average Velocity and average Speed

Unit 5: Motion and Forces


Everything moves. Even apparently stationary things, such as a buildings, move with Earth’s rotation. Earth orbits around the Sun, the Sun orbits around the center of the Milky Way galaxy, and that galaxy migrates relative to other galaxies. The classification and comparison of motions (called kinematics) is challenging. What exactly do you measure, and how do you compare?
Here, we will examine some general properties of motion that is restricted in three ways.
1. The motion is along a straight line only. The line may be vertical, horizontal, or slanted, but it must be straight.
2. Forces (pushes and pulls) cause motion. We discuss only the motion itself and changes in the motion.
Questions we answer: Does the moving object speed up, slow down, stop, or reverse direction? If the motion does change, how is time involved in the change?
3. The moving object is either a particle (by which we mean a point-like object such as an electron) or an object that moves like a particle (such that every portion moves in the same direction and at the same rate). A ball falling down might be considered to be moving like a particle; however, if the ball is spinning it would not.

Concept by Kishore Lal. Programmed by Kishore Lal... Copyright © 2015 Kishore Lal. All rights reserved.