Question 2.2: SLOWLY MOVING TRAIN GOAL Obtain average and instantaneous ve...
SLOWLY MOVING TRAIN
GOAL Obtain average and instantaneous velocities from a graph.
PROBLEM A train moves slowly along a straight portion of track according to the graph of position vs. time in Figure 2.7a. Find (a) the average velocity for the total trip, (b) the average velocity during the first 4.00 s of motion, (c) the average velocity during the next 4.00 s of motion, (d) the instantaneous velocity at t = 2.00 s, and (e) the instantaneous velocity at t = 9.00 s.
STRATEGY The average velocities can be obtained by substituting
the data into the definition. The instantaneous velocity at t = 2.00 s
is the same as the average velocity at that point because the position
vs. time graph is a straight line, indicating constant velocity. Finding
the instantaneous velocity when t = 9.00 s requires sketching a line
tangent to the curve at that point and finding its slope.
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