Velocity
- Time Graphs
These
represent how the velocity of an object changes as time progresses.
Time (as always!)
is on the x-axis and displacement on the y-axis.
You may be given data
and asked to plot a graph
or you may be asked to interpret of sketch one. You should be able to
do all of these things.
Rather than 'learn'
these graphs you should aim to understand them. Talk yourself through
what the line represents in terms of 'the object starts off travelling
at 'so many metres per second' at t=0 seconds and then is at 'such and
such velocityr' by the next second....' etc. You can then tell whether
it is speeding up of slowing down.
The gradient of the
line represents the acceleration. You need to know how to work out a gradient
and show how you have done it. Do NOT just write down an answer.
The area under the
graph represents the distance travelled. Break this up into stages if
necessary to give yourself a series of triangles and rectangles to find
the area of. Always mark out what you are doing clearly for the examiner,
so that s/he can follow what you are doing!
Sometimes you may be expected
to find the gradient of a straight portion of a curved graph. If this is
the case extend the straight line (extrapolate it!) so that you can use
a large triagle to find the gradient.
LOJ
March 2003