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boland (kbb544) – HW3 – Mackie – (10611)
1
This printout should have 17 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
(part 1 oF 2) 10.0 points
A particle travels horizontally between two
parallel walls separated by 18
.
4 m. It moves
toward the opposing wall at a constant rate
oF 7
.
8 m
/
s. Also, it has an acceleration in the
direction parallel to the walls oF 4
.
1 m
/
s
2
.
18
.
4 m
4
.
1 m
/
s
2
7
.
8 m
/
s
What will be its speed when it hits the
opposing wall?
Correct answer: 12
.
4251 m
/
s.
Explanation:
Let :
d
= 18
.
4 m
,
v
x
= 7
.
8 m
/
s
,
a
= 4
.
1 m
/
s
2
,
Basic Concepts
Kinematics equations
v
=
v
o
+
g t
s
=
s
o
+
v
o
t
+
1
2
g t
2
d
a
9
67179 m
7
.
8 m
/
s
12
4251 m
38
8851
◦
11
.
4078 m
The horizontal motion will carry the parti
cle to the opposite wall, so
d
=
v
x
t
f
and
t
f
=
d
v
x
=
(18
.
4 m)
(7
.
8 m
/
s)
= 2
.
35897 s
.
is the time For the particle to reach the oppo
site wall.
Horizontally, the particle reaches the maxi
mum parallel distance when it hits the oppo
site wall at the time oF
t
=
d
v
x
,
so the fnal
parallel velocity
v
y
is
v
y
=
a t
=
a d
v
x
=
(4
.
1 m
/
s
2
) (18
.
4 m)
(7
.
8 m
/
s)
= 9
.
67179 m
/
s
.
The velocities act at right angles to each
other, so the resultant velocity is
v
f
=
r
v
2
x
+
v
2
y
=
r
(7
.
8 m
/
s)
2
+ (9
.
67179 m
/
s)
2
=
12
.
4251 m
/
s
.
002
(part 2 oF 2) 10.0 points
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View Full Document boland (kbb544) – HW3 – Mackie – (10611)
2
At what angle with the wall will the particle
strike?
Correct answer: 38
.
8851
◦
.
Explanation:
When the particle strikes the wall, the ver
tical component is the side adjacent and the
horizontal component is the side opposite the
angle, so
tan
θ
=
v
x
v
y
,
so
θ
= arctan
p
v
x
v
y
P
= arctan
p
7
.
8 m
/
s
9
.
67179 m
/
s
P
=
38
.
8851
◦
.
Note:
The distance traveled parallel to the
walls is
y
=
1
2
a t
2
=
1
2
(4
.
1 m
/
s
2
) (2
.
35897 s)
2
= 11
.
4078 m
.
003
(part 1 of 3) 10.0 points
A ball of mass 0
.
6 kg, initially at rest, is
kicked directly toward a fence from a point
20 m away, as shown below.
The velocity of the ball as it leaves the
kicker’s foot is 16 m
/
s at angle of 47
◦
above
the horizontal. The top of the fence is 4 m
high. The ball hits nothing while in Fight and
air resistance is negligible.
The acceleration due to gravity is 9
.
8 m
/
s
2
.
b
20 m
4 m
16 m
/
s
47
◦
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
b
Determine the time it takes for the ball to
reach the plane of the fence.
Correct answer: 1
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This note was uploaded on 02/20/2011 for the course PHYS 1062 taught by Professor Mackie during the Spring '11 term at Temple.
 Spring '11
 MACKIE
 Physics

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