reddy (ar38357) – Tension and inclined planes – clancy – (SCI4112)
1
This printout should have 9 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
10.0 points
Can an object be in mechanical equilibrium
when only a single Force acts on it? Explain.
1.
None oF these
2.
No; even one Force is too much. There
should be no Forces acting on an object.
3.
No; at least one other Force is needed to
cancel the action oF the frst Force.
correct
4.
Yes; a single Force is necessary to keep the
object in mechanical equilibrium.
5.
Yes; the object will act back with an equal
and opposite Force.
Explanation:
The sum oF the Forces acting on an object
in equilibrium has to equal zero. Since only a
single Force acts on the object, it cannot be in
equilibrium.
002
(part 1 oF 2) 10.0 points
The wind exerts a Force oF 290 N North on
a sailboat, while the water exerts a Force oF
129 N West on the sailboat.
What is the magnitude oF the net external
Force on the sailboat?
Correct answer: 317
.
397 N.
Explanation:
Let :
F
x
=
F
water
=
−
129 N
and
F
y
=
F
wind
= 290 N
.
290 N
129 N
v
Scale: 100 m
θ
Thus
F
net
=
r
F
2
x
+
F
2
y
=
r
(
−
129 N)
2
+ (290 N)
2
=
317
.
397 N
.
003
(part 2 oF 2) 10.0 points
How many degrees west oF north is this net
external Force directed?
Correct answer: 23
.
9808
◦
.
Explanation:
tan
θ
=
F
x
F
y
θ
= tan
−
1
p
F
x
F
y
P
= tan
−
1
p
−
129 N
290 N
P
=
−
23
.
9808
◦
,
which is 23
.
9808
◦
to the west oF north.
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2
004
10.0 points
Two men decide to use their cars to pull a
truck stuck in mud. They attach ropes and
one pulls with a force of 982 N at an angle
of 30
◦
with respect to the direction in which
the truck is headed, while the other car pulls
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 Fall '10
 Sontar
 Physics, Force, kg, net external force, Inclined Planes

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