homework 08 – RAHMAN, TARIQUE – Due: Feb 20 2008, 3:00 am
1
Question 1, chap 6, sect 1.
part 1 of 2
10 points
A block of mass
m
is accelerated across a
rough surface by a force of magnitude
F
that
is exerted at an angle
φ
with the horizontal,
as shown above.
The frictional force on the
block exerted by the surface has magnitude
f
.
f
F
φ
m
What is the magnitude of the acceleration
vectora
of the block?
1.

vectora

=
F
m
2.

vectora

=
F
cos
φ

f
m
3.

vectora

=
F

f
m
4.

vectora

=
F
cos
φ
m
5.

vectora

=
F
sin
φ

m g
m
Question 2, chap 6, sect 1.
part 2 of 2
10 points
Which of the following expressions for the
coefficient of friction is correct?
1.
μ
=
m g
f
2.
μ
=
f
m g

F
cos
φ
3.
μ
=
f
m g

F
sin
φ
4.
μ
=
f
m g
5.
μ
=
m g

F
cos
φ
f
Question 3, chap 6, sect 1.
part 1 of 3
10 points
A block is at rest on the incline shown
in the figure.
The coefficients of static and
kinetic friction are
μ
s
= 0
.
87 and
μ
k
= 0
.
74,
respectively.
The acceleration of gravity is 9
.
8 m
/
s
2
.
27 kg
μ
37
◦
What is the frictional force acting on the
27 kg mass?
Answer in units of N.
Question 4, chap 6, sect 1.
part 2 of 3
10 points
What is the largest angle which the incline
can have so that the mass does not slide down
the incline?
Answer in units of
◦
.
Question 5, chap 6, sect 1.
part 3 of 3
10 points
What is the acceleration of the block down
the incline if the angle of the incline is 44
◦
?
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