Ch 2 : kinematics Ideas about describing motion: speed, velocity, acceleration

Kinematics Ave speed: s = total distance/total time Run 3 miles at 10 mi/hr, then crawl 3 miles at 1 mi/hr. What is your average speed?

Kinematics Speed vs. velocity These words often are used interchangeably but there is a difference. Velocity is a vector, meaning it has direction. Speed is just how fast something is traveling.

Kinematics Acceleration: a word we use frequently but is often misunderstood. Acceleration: how the velocity of something is changing. It’s the rate of change of a rate of change (huh?) A speed of 1 m/s is very different from an acceleration of 1m/s/s. We will only solve problems which have constant or uniform acceleration

Kinematics Importance of graphing and being able to interpret graphical data concerning motion. A graph gives you a quick representation. Slopes of graphs tell you rates: slope of a distance/time graph gives you speed, slope of a velocity/time graph gives you acceleration.

Kinematics Whenever possible make a quick graph of a motion problem. A velocity/time graph can be used to find distance (often easier than plugging in numbers into equations). The area under a velocity/time graph gives you the distance travelled.

Kinematics “standard equations” for motion at constant acceleration V = v 0 + at X = x 0 + v 0 t + ½ a t 2 V 2 = v a (x – x 0 ) V(ave) = (v + v 0 )/2 Which equation you use depends on what you know.