Finding Speed:Slow or Fast Video Lecture - Class 7

okay so what is speed it seems obvious
it's how fast you traveling but let's
think about this a little bit further
little bit deeper let's take two cars
one is speeding the other is not what's
the difference between those two cars I
top explain this and we'll introduce you
to Sammy Sammy the super sale she goes
for a slide how can we figure out how
fast she's traveling I can figure out
her speed we need to know two things one
we need to know how far she's traveled
we're gonna call this distance and we
need to know how much time she took to
cover this distance using these two
figures for example Sammy covers 10
meters we're going to use meters here
because to scientists these are the most
useful units she covers the 10 meters in
10 seconds we're going to do seconds
also because they're very useful so how
fast does she travel we take the
distance 10 meters and divide by the
time 10 seconds 10 divided by 10 is 1
meter per second ok the next day after
eaten away through my lettuces she does
the same 10 meters but in 5 seconds is
she faster or slower well let's find out
we take the distance in meters 10 meters
divided by the time in seconds 5 10
divided by 5 is 2 meters per second
which is twice as fast obviously very
delighted with this ok so let's go back
to the cars the speeding car will be
covering the same distance in less time
compared to the safe motorist although
scientists prefer m/s any combination of
distance and time depending on what's
useful to you would be acceptable so for
example if we want to know how fast a
tectonic plates move against each other
we could use a unit more like
centimeters per year but it'd still be
acceptable