[问答题]
Figure 2–43 shows the
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zhvn6 ds7x((bd7c2g7 m6bzckcycles, A and B. (a) Is there any instant at which the two bicycles have the same velocity? (b) Which bicycle has the larger acceleration? (c) At which instant(s) are the bicycles passing each other? Which bicycle is passing the other? (d) Which bicyc
n7bsmdbg7c7 dz( 2kc66 hv(xz le has the highest instantaneous velocity? (e) Which bicycle has the higher average velocity?
参考答案:
(a) The two bicycles will have the same velocity at any
time when the instantaneous
slopes of their x vs. t graphs are the same. That occurs near the time t1 as marked on the graph.
(b) Bicycle A has the larger
acceleration, because
its graph is concave upward,
indicating a positive
acceleration. Bicycle B has no acceleration because its
graph has a constant slope.
(c) The bicycles are passing
each other at the times
when the two graphs cross,
because they both have the same position at that time. The graph with the steepest slope is the
faster bicycle, and so is the one that is passing at that instant. So at the first crossing, bicycle B is
passing bicycle A. At the second
crossing, bicycle A is passing bicycle B.
(d) Bicycle
B has the highest instantaneous velocity at all times until the time t1., where both graphs have
the same slope. For all times after t1, bicycle A has the highest
instantaneous velocity. The largest
instantaneous velocity is for bicycle A at the latest time shown on the graph.
(e) The bicycles appear to
have the same average velocity. If the
starting point of the graph for a
particular bicycle is
connected to the ending point with a straight line, the slope of that line is
the average velocity. Both appear to
have the same slope for that “average” line.
本题详细解析:
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