Distance Time Graphs Video Lecture - Class 9

science shorts gives you speed and
distance time graphs this will be in p3
for those of you doing OCR GCSE science
p2 for AQA and topic 15 for Edexcel it's
ridiculously easy to get mixed up
between distance time graphs and speed
time graphs if you're not concentrating
you can trip up and in your exam lose
out on some easy marks that's why it's
being split up into two videos here
okay here's Bob Bob has a tank and he's
about to roll down to the YouTube HQ to
offer his opinion on forcing everyone to
use Google Plus which is just great so
offi tunnels and he covers the first 50
meters in 10 seconds to draw this on a
speed time graph we start at zero eaters
and zero seconds and draw a straight
line into 50 meters and 10 seconds Bob
then hit some traffic so naturally it
takes a bit of extra time to get over
the cars over the next 20 seconds he
only moves 20 meters so we draw a line
now going to 70 meters and 30 seconds
after the traffic he pegs the final
stretch of 30 meters in five seconds so
we now finish our graph at 100 meters
and 35 seconds now let's have a look at
our graph let's try to calculate Bob's
speed and different points now speed is
measured in meters per second M / S
that's how we write it we should give
you a clue as to how we actually
calculate it speed is of course equals
to distance divided by time or you might
say your distance over time that means
if you know how long it took for
something to travel a certain distance
you can calculate in speed look at it
Bob's first part of the journey we can
see he traveled 50 meters in 10 seconds
that means his speed is 5 meters per
second what we've just done is
calculated the gradient of this bit of
the graph put simply gradient is just up
/ across using two points on a graph
that's quite important though that the
gradient of a distance time graph is
equals to this beat or we might say
average speed okay so it's your turn now
pause the video and calculate Bob speed
during the next two
parts of his journey let's see how you
got on then he took 20 seconds to go
over 20 metres of cars so the gradient
equals 20 meters divided by 20 seconds
so his speed is 1 meter per second
the final stretch of 30 meters took in 5
seconds so 30 meters divided by 5
seconds equals 6 meters per second well
done if you got those right of course if
there was a horizontal line on this
distance time graph that would mean that
Bob would not be moving for that period
of time as his distance actually isn't
increasing to learn about speed time
graphs and acceleration and whether Bob
escapes click here or follow the link in
the description don't forget to leave a
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