Describing and measuring motion (Describing motion (reference points…
Describing and measuring motion
a reference point is a place or object used for comparison to determine if something is in motion.
these are things that stay in one place/still
scientists use the same system of measurement called the International System of Units also called the System International. (SI)
scientists use SI units to describe the distance an object moves
scientists will use SI units to describe quantities other than length.
when you measure distance you measure length.
The SI unit of length is a meter.
the meter is a little longer than a yard.
if the length is smaller than a meter they will centimeters
the prefix of centi means one hundredth
there are 100 centimeters in a meter.
for lengths smaller than a centimeter scientist will use a millimeter
the prefix for milli means one thousand
there are 1000 millimeters in a meter
for distances too long to be measured in meters scientist will use Kilometers
the prefix for kilo means one thousand
there are meters in a kilometer.
relative to the sun we are moving but because you are moving with earth you do not seem to be moving.
an object is in motion if it changes position or relative to a reference point.
The speed of most moving objects is not constant.
to calculate the average speed divide the total distance traveled by the total time.
the rate an object is moving at a given instant in time.
to calculate the speed of an object divide the distance the object travels by the amount of time.
if you know the distance an object travels in a certain amount of time you can calculate the speed of an object.
speed is a type of rate.
a rate tells us the amount of something that occurs or changes in one unit of time.
when you know both the speed and direction of an objects motion you know the velocity of the object.
velocity is also important in airplane pilots.
to avoid colliding with another aircraft pilots must have precise control of their speed and direction.
the horizontal line in segment 2 shows how the jogger's distance did not change at all.
you can calculate the slope of a line by dividing the rise by the run.
the rise is the vertical difference between the point and the run is the horizontal difference.