Ch.5, Sec.1 – Measuring Motion motion: an object’s change in position relative to a reference point - objects that appear to stay in place are called reference points (e.g. Earth, trees, etc…) Speed Depends on Distance & Time speed: the distance traveled divided by the time interval during which the motion occurred

Ch.5, Sec.1 – Measuring Motion the SI unit for speed is meters per second (m/s) - most moving objects do not move at a constant speed, so average speed is often calculated instead: average speed = total distance total time Velocity: Direction Matters velocity: the speed of an object in a particular direction speed and velocity are different, as velocity must include a reference direction!!! an object’s velocity changes if speed or direction changes

Ch.5, Sec.1 – Measuring Motion see figure 4 on page 121 for combining velocities to equal resultant velocities Acceleration acceleration: the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change the faster the velocity changes, the greater the acceleration is; the slower the velocity changes, the greater the deceleration is - average acceleration can be found by using the following equation: avg. acceleration = final velocity – starting velocity time it takes to change velocity