Chapter 2: Motion along a Straight Line
Example Questions & Problems
Example 2.1
An automobile travels on a straight road for 40 km at 30 km/h. It then continues in the same
direction for another 20 km at 60 km/h. Assume an instantaneous change in speed. (a) What is
the average speed of the car during this 60 km trip? (b) Draw a motion diagram and plot x vs. t
and indicate how the average speed is found on the plot.
Example 2.2
For each part, draw a motion diagram, plot (x, vx, ax) vs. t, and explain your reasoning.
a. John leaves home in Santa Cruz and travels south at a steady 60 mph. Jane, 350 miles to
the South in Los Angles, leaves at the same time and travels north at a steady 40 mph.
Where will they meet for lunch?
b. A particles position is given by the plot (do not plot ax vs. t).
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c. A basketball player starts at the left end of the court and moves with the velocity shown.
Example 2.3
You apply your brakes on your Porsche from a velocity of 85 km/hr to 45 km/hr over a distance
of 105 m.
a. Draw a motion diagram and plot (x, vx, ax) vs. t for the situation
b. (i) What are the acceleration and (ii) how much time elapses during this interval?
c. If you continue to brake, how much longer and how far would you go?
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Example 2.4
Maria is running at 9 m/s but is 40 m behind Juan. Juan is starting from rest on his motorbike
that accelerates at 0.9 m/s2.
a. Draw a motion diagram and plot (x, vx, ax) vs. t for the situation.
b. Where and how long does it take for Maria catches Juan? What is the time interval during
which Maria remains ahead of Juan?
c. How fast is Juan going when Maria catches Juan? How fast is Juan traveling when he
passes Maria?
Example 2.5
An elevator cab in the New York Marquis Marriott has a total run of 190 m. Its maximum speed
is 305 m/min. Its acceleration and deceleration both have a magnitude of 1.22 m/s2.
a. Draw a motion diagram and plot (y, vy, ay) vs. t for the situation.
b. How far does the cab move while accelerating to full speed from rest?
c. How long does it take to make the nonstop 190 m run, starting and ending at rest?
Example 2.6
A model rocket fired vertically from the ground ascends with a constant vertical acceleration of
4.00 m/s2 for 6.00 s. Its fuel is then exhausted.
a. Draw a motion diagram and plot (y, vy) vs. t for the situation.
b. What is the maximum altitude reached?
c. What is the total time elapsed from takeoff until the rocket strikes the ground?
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