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Unformatted text preview: Physics 121
Name 9/ 1 4/07
Section 1. A ball rolls up and back down a
straight incline as shown. In the
following, assume that the xaxis is
along the incline positive to the right. a. On the axes provided, sketch qualitatively correct graphs of
position vs. time, velocity vs. time, and acceleration vs. time for
the motion of the ball up and back down the incline. (Get the
shapes right, but don’t worry about numbers. Be sure to assume
the same time scale for each graph, though.) (6 points) (b)(e) lt’s observed that the ball'begins up the incline with a
speed of 6.0 m/s, and slows down at a constant rate to 2.0 m/s in 8.0 s. (That encompasses only part of the motion up the incline,
of course.) b. What’s the speed of the ball 0.50 s after it begins up the incline? (2 points) ‘v 8.0: I. Exam 1 Turnaround
K point 9.9;, a; a riﬂe/st c. At what time does the ball turn around? (2 points) . E
4’ ‘0 V: of“ Md'v;
lam/3’ ’2) S7“! '
’5 d. At half of that time (your result for a has the ball traveled
halfivay t0 the turnaround point, more than halfivay t0 the
turnaround point, or less than halfivay t0 the turnaround point? Explain your reasoning. (2 points) . ,. 0" “J A Just? 6 .r so
50 uLu {4 0w". a. e. Determine how far up the incline me Ball trav . points) ff? J “was
)M'r‘(6*u)/“: 30
,ct *I? ' I ___1__.;_..__A__.__..__: Name Section 2. An object moves with constant acceleration
according to the position vs. time graph at right. For (a)(e), give the time, or interval of time, during
which the object’s motion ﬁts the given description.
(If the object never moves as described, say so
explicitly.) In each case, brieﬂy explain your
reasoning. a. The object has positiv velocity. (2 points)
2 r: in s a"
—I% ’ a34 b. The object has positive acceleration. (2 poi ) O— 5: —«v Slowly {m Ol: c. The object 1s speeding up. (2 points), _+Q. d. The object has zero velocity. ( points) if ’04». e. The object has zero acceleration. (2 points) ~ ' b
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f. Determine the average velocity for the entire motion. 3 points) «=Aoc_n—g
” a? " f: g. Is the average speed for the entire motion greater than, less than, or equal to the magnitude of the average velocity for the entire motion? Explain. (2 pom 3700.]: Name Section 3. An object moves along a line according to the velocity vs. time graph below. a. On the axes below create a graph of acceleration vs. time for this motion. Make it quantitatively correct; i.e.,
get the numbers right. (5 points) *VN [3* 01:: 3 "" b. How far does the object travel during the entire motion? (5 points) am; 5v.“ v.94. UMP'1
.32" Name Section 4. Train platform. You want to visit your friend in New York over winter break. To save money, you decide to
travel there by train. But you are late ﬁnishing your physics ﬁnal, so you are late in arriving at the train station.
You run as fast as you can, but just as you reach one end of the platform, your train is 30 meters ahead of you
down the platform and traveling at a constant speed of 5.0 m/s. You run at your top speed of 8.0 m/s. You can
run along the platform for 50 meters before you reach a barrier. Will you catch your train? (For full credit your
solution must include qualitatively correct graphs of position vs. time and velocity vs. time, a description of
your plan for solving the problem, and an answer to the question posed in the problem points) . 'ﬁofar you.
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 Fall '07
 Angerson

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