Version 050 – Exam1 – markert – (56480)
1
This
printout
should
have
14
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001
10.0 points
A rock is thrown downward from an unknown
height above the ground with an initial speed
of 24 m
/
s. It strikes the ground 8
.
6 s later.
Determine the initial height of the rock
above the ground. The acceleration of gravity
is 9
.
8 m
/
s
2
.
1. 327.236
2. 513.6
3. 568.804
4. 33.649
5. 88.704
6. 283.296
7. 296.704
8. 254.464
9. 144.624
10. 491.404
Correct answer: 568
.
804 m.
Explanation:
Consider down to be positive.
Let :
g
= 9
.
8 m
/
s
2
,
v
0
= 24 m
/
s
,
and
t
= 8
.
6 s
.
h
=
h
0

v
0
t

1
2
g t
2
= 0
h
0
=
v
0
t
+
1
2
g t
2
= (24 m
/
s) (8
.
6 s) +
1
2
(9
.
8 m
/
s
2
) (8
.
6 s)
2
=
568
.
804 m
.
002
10.0 points
The graph shows the velocity
v
as a function
of time
t
for an object moving in a straight
line.
t
v
0
t
Q
t
R
t
S
t
P
Which graph shows the corresponding dis
placement
x
as a function of time
t
for the
same time interval?
1.
t
x
0
t
Q
t
R
t
S
t
P
2.
t
x
0
t
Q
t
R
t
S
t
P
3.
t
x
0
t
Q
t
R
t
S
t
P
correct
4.
t
x
0
t
Q
t
R
t
S
t
P
5.
t
x
0
t
Q
t
R
t
S
t
P
6.
t
x
0
t
Q
t
R
t
S
t
P
7.
t
x
0
t
Q
t
R
t
S
t
P
8.
None of these graphs is correct.
9.
t
x
0
t
Q
t
R
t
S
t
P
Explanation:
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Version 050 – Exam1 – markert – (56480)
2
The displacement is the integral of the ve
locity with respect to time:
vectorx
=
integraldisplay
vectorv dt .
Because the velocity increases linearly from
zero at first, then remains constant, then de
creases linearly to zero, the displacement will
increase at first proportional to time squared,
then increase linearly, and then increase pro
portional to negative time squared.
From these facts, we can obtain the correct
answer.
t
x
0
t
Q
t
R
t
S
t
P
003
10.0 points
A hunter wishes to cross a river that is 1
.
51 km
wide and flows with a speed of 2
.
19 km
/
h
parallel to its banks. The hunter uses a small
powerboat that moves at a maximum speed
of 9
.
13 km
/
h with respect to the water.
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 Fall '08
 Swinney
 Velocity, 1 km, 5 m, 2 m, 1 1 G, 6 1m

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