armington (kma786) – hw0201 – fete – (57165)
1
This printout should have 15 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
10.0 points
IF you drop an object, it will accelerate down
ward at a rate oF
g
= 9
.
8 m
/
s
2
.
IF you throw it downward instead, its accel
eration (in the absence oF air resistance) will
be
1.
less than 9
.
8 m
/
s
2
.
2.
9
.
8 m
/
s
2
correct
3.
greater than 9
.
8 m
/
s
2
.
4.
Unable to determine.
Explanation:
The acceleration due to the gravity is in
dependent oF any initial velocity and remains
constant.
002
10.0 points
A stone is thrown straight upward and at the
top oF its trajectory its velocity is momentar
ily zero.
What is its acceleration at this point?
1.
9.8 m/s
2
down
correct
2.
Unable to determine
3.
9.8 m/s
2
up
4.
Zero
Explanation:
The gravitational acceleration near the sur
Face oF the earth is considered constant For all
practical purposes. This acceleration oF 9.8
m/s
2
points downward.
003
10.0 points
A basketball player achieves a hang time oF
0
.
94 s in dunking the ball.
What vertical height will he attain? The
acceleration oF gravity is 9
.
8 m
/
s
2
.
Correct answer: 1
.
08241 m.
Explanation:
Let :
t
= 0
.
94 s
and
g
= 9
.
8 m
/
s
2
.
It takes the basketball player Δ
t
=
t
2
to
rise to his maximum height, defned by
h
=
1
2
g
(Δ
t
)
2
=
g
2
t
2
4
=
g t
2
8
=
(9
.
8 m
/
s
2
) (0
.
94 s)
2
8
=
1
.
08241 m
.
004
10.0 points
The acceleration oF a marble in a certain ±uid
is proportional to the speed oF the marble
squared, given by
a
=
α v
2
,
where
v >
0 m/s and
α
=

1
.
61 m
−
1
.
IF the marble enters this ±uid with a speed
oF 0
.
96 m
/
s, how long will it take beFore the
marble’s speed is reduced to halF oF its initial
value?
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 Spring '07
 Swinney
 mechanics, Acceleration, Velocity, Correct Answer, m/s

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