Hood, Charles – Homework 4 – Due: Oct 5 2006, 11:00 pm – Inst: Jan Opyrchal
1
This
printout
should
have
9
questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
The due time is Central
time.
001
(part 1 oF 3) 10 points
A particle moves in the
xy
plane with constant
acceleration.
At time zero, the particle is
at
x
= 3
.
5 m,
y
= 3 m, and has velocity
~v
o
= (1 m
/
s) ˆ
ı
+(

3 m
/
s) ˆ
.
The acceleration
is given by
~a
= (1
.
5 m
/
s
2
) ˆ
ı
+ (2 m
/
s
2
) ˆ
.
What is the
x
component oF velocity aFter
8
.
5 s?
Correct answer: 13
.
75 m
/
s.
Explanation:
Let :
a
x
= 1
.
5 m
/
s
2
,
v
xo
= 1 m
/
s
,
and
t
= 8
.
5 s
.
AFter 8
.
5 s,
~v
x
=
~v
xo
+
~a
x
t
= (1 m
/
s) ˆ
ı
+ (1
.
5 m
/
s
2
) ˆ
ı
(8
.
5 s)
=
(13
.
75 m
/
s) ˆ
ı
.
002
(part 2 oF 3) 10 points
What is the
y
component oF velocity aFter
8
.
5 s?
Correct answer: 14 m
/
s.
Explanation:
Let :
a
y
= 2 m
/
s
2
and
v
yo
=

3 m
/
s
.
~v
y
=
~v
yo
+
~a
y
t
= (

3 m
/
s) ˆ
+ (2 m
/
s
2
) ˆ
(8
.
5 s)
=
(14 m
/
s) ˆ
.
003
(part 3 oF 3) 10 points
What is the magnitude oF the displacement
From the origin (
x
= 0 m,
y
= 0 m) aFter
8
.
5 s?
Correct answer: 82
.
8 m.
Explanation:
Let :
d
o
= (3
.
5 m
,
3 m)
,
v
o
= (1 m
/
s
,

3 m
/
s)
,
and
a
= (1
.
5 m
/
s
2
,
2 m
/
s
2
)
.
±rom the equation oF motion,
~
d
=
~
d
o
+
~v
o
t
+
1
2
a t
2
=
h
(3
.
5 m) ˆ
ı
+ (3 m) ˆ
i
+ [(1 m
/
s) ˆ
ı
+ (

3 m
/
s) ˆ
] (8
.
5 s)
+
1
2
h
(1
.
5 m
/
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 Fall '08
 KEN
 Acceleration, Work, Velocity, Correct Answer, m/s, Hood

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