Describing & Measuring Motion

Recognizing Motion  Motion  The state in which one object’s distance from another is changing.  Even though you are sitting still right now you are actually moving 30 kilometers every second  Whether an object is moving or not depends on your POINT OF VIEW. Unit of Force = Newtons (N)

Recognizing Motion  Reference Point  A place or object used for comparison to determine if something is in motion.  An object is in motion if it changes position relative to a reference point.  You assume that the reference point is stationary, or not moving, however it is also in motion.

Describing Distance  To describe motion further, you need to use units of measurements.  2 cups of milk  Run 100 yards  Buy 3 pounds of fruit  International System of Units (SI)  A system of measurement based on multiples of ten and on established measures of MASS, LENGTH, and TIME.  To help communicate information clearly scientists all over the world use them same system of units.

Describing Distance  Meter  Basic SI unit of length  SI units area also used to describe quantities such as volume (liter-L) and mass (grams-g)

Calculating Speed  Speed  The distance an object travels in one unit of time.  Constant Speed  Movement at a fixed (constant) distance per unit of time.  Average Speed  Total distance covered over a time interval.

Calculating Speed  Average Speed Examples  A cyclist changes their speed many times during a race. Climb up steep inclines, glide alone level ground, dash down hills, etc.  A racecar driver changes speed many times during a race. Around sharp corners, straight a ways, pit stops, etc.  You find the average speed by adding up the speeds and adding up the times and then divide the two #’s.  Most objects do not travel at a constant speed very long.  Constant Speed Examples  A ship traveling across the ocean may move at the same speed for several hours.  A horse cantering across a field may keep at a steady pace for several minutes.  Anything that travels at a speed that doesn’t change is traveling at a constant speed.  The speed is always the same at all times during motion.

Describing Velocity  It is important to not only know the speed of things but also direction  Velocity  When you know both speed in direction of an objects motion.  Air traffic controllers must know the velocity of aircrafts  Forecasters must the velocity of thunderstorms, snowstorms, etc.  Stunt pilots use velocity to prevent collisions and make graceful maneuvers

Describing Velocity  Benz Tricycle Car  15 km/h  Transcontinental Railroad  30 km/h  Interstate Highway System  100 km/h  TGV in Motion  300 km/h  Ford Model T  65 km/h  Pioneer Zephyr  125 km/h

Graphing Motion  You represent motion with a line graph.  Y-axis = distance  X-axis = time  Each point on the graph represents the location of the object at a particular time.  A straight line (a line with a constant slant, or slope) represents motion at a constant speed.  The steepness of the slope depends on how quickly or slowly the object is moving.  The faster the motion, the steeper the slope.  A horizontal line represents an object that is not moving at all.