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fingernails scratching on a chalkboard. We say that this is a graph of “x
versus t.” If the axes were the other way around, it would be a graph of “t
versus x.” I remember the “versus” terminology by visualizing the labels on
the x and t axes and remembering that when you read, you go from left to
right and from top to bottom.
Discussion questions
A. An ant walks forward, pauses, then runs quickly ahead. It then suddenly
reverses direction and walks slowly back the way it came. Which graph could
represent its motion.
xxx
xxx
ttt
ttt
1
2
3
4
5
6
B. The figure shows a sequence of positions for two racing tractors. Compare
the tractors’ velocities as the race progresses. When do they have the same
velocity.
t=0 st=1 st=2 st=3 st=4 st=5 st=6 st=7 s
t=0 st=1 st=2 st=3 st=4 st=5 st=6 st=7 s
C. If an object had a straight-line motion graph with
.
x=0 and
.
t
.
0, what would
be true about its velocity. What would this look like on a graph. What about
.
t=0 and
.
x
.
0.
D. If an object has a wavy motion graph like the one in example (e) on the
previous page, which are the points at which the object reverses its direction.
What is true about the object’s velocity at these points.
E. Discuss anything unusual about the following three graphs.
Chapter 2Velocity and Relative Motion