practice 06 – ALIBHAI, ZAHID
1
Latest unpenalized work: Feb 25 2007 Sunday
04:00 (after this date you can not make a
perfect score). Work cutoff: Feb 25 2007, 4:00
am.
Question 1
part 1 of 3
10 points
A block starts at rest and slides down a
frictionless track except for a small rough area
on a horizontal section of the track (as shown
in the figure below).
It leaves the track horizontally, flies through
the air, and subsequently strikes the ground.
The acceleration of gravity is 9
.
81 m
/
s
2
.
μ
=0
.
3
1
.
2 m
500 g
h
1
.
9 m
3
.
42 m
9
.
81 m
/
s
2
v
At what height
h
above the ground is the
block released?
Answer in units of m.
Question 2
part 2 of 3
10 points
What is the the speed of the block when it
leaves the track?
Answer in units of m
/
s.
Question 3
part 3 of 3
10 points
What is the total speed of the block when
it hits the ground?
Answer in units of m
/
s.
Question 4
part 1 of 3
10 points
A block of mass
m
is pushed a distance
D
up an inclined plane by a horizontal force
F
.
The plane is inclined at an angle
θ
with
respect to the horizontal.
The block starts
from rest and the coefficient of kinetic friction
is
μ
k
.
m
D
μ
k
F
θ
If
N
is the normal force, what is the work
done by friction?
1.
W
=

μ
k
N
D
2.
W
=

μ
k
(
N 
m g
cos
θ
)
D
3.
W
= +
μ
k
(
N
+
m g
cos
θ
)
D
4.
W
=

μ
k
(
N
+
m g
cos
θ
)
D
5.
W
= +
μ
k
(
N 
m g
cos
θ
)
D
6.
W
= 0
7.
W
= +
μ
k
N
D
Question 5
part 2 of 3
10 points
What is the work done by the normal force
N
?
1.
W
=
N
D
sin
θ
2.
W
=
N
D
3.
W
= (
N
+
m g
cos
θ
+
F
sin
θ
)
D
4.
W
=
N
D
5.
W
= (
m g
cos
θ
+
F
sin
θ
 N
)
D
6.
W
=
N
D
cos
θ
7.
W
= (
N 
m g
cos
θ

F
sin
θ
)
D
8.
W
= 0
Question 6
part 3 of 3
10 points
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practice 06 – ALIBHAI, ZAHID
2
What is the final speed of the block?
1.
v
=
radicalbigg
2
m
(
F
cos
θ

m g
sin
θ
+
μ
k
N
)
D
2.
v
=
radicalbigg
2
m
(
F
cos
θ

m g
sin
θ

μ
k
N
)
D
3.
v
=
radicalbigg
2
m
(
F
sin
θ
+
μ
k
N
)
D
4.
v
=
radicalbigg
2
m
(
F
cos
θ
+
m g
sin
θ
)
D
5.
v
=
radicalbigg
2
m
(
F
sin
θ

μ
k
N
)
D
6.
v
=
radicalbigg
2
m
(
F
cos
θ
+
m g
sin
θ

μ
k
N
)
D
7.
v
=
radicalbigg
2
m
(
F
cos
θ

μ
k
N
)
D
8.
v
=
radicalbigg
2
m
(
F
cos
θ

m g
sin
θ
)
D
Question 7
part 1 of 1
10 points
A 0
.
3 kg mass is initially at rest and is free
to move with negligible friction along the
x

axis. The figure below shows the value of an
applied force as a function of time.

1
0
1
2
3
4
5
0
1
2
3
4
5
6
7
8
9
10
time ( s )
Δ
t
Force ( N )
Calculate the kinetic energy
K
of the mass
when it reaches 5 s.
Answer in units of J.
Question 8
part 1 of 1
10 points
An outboard motor propels a boat through
the water at 14 mi
/
h.
The water resists the
forward motion of the boat with a force of
8 lb.
How much power is produced by the motor?
Answer in units of hp.
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 Spring '08
 Turner
 Force, Friction, Mass, Potential Energy, Work, ZAHID Question

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