chauhan (mmc2762) – Ch5H1 – turner – (56910)
1
This
printout
should
have
18
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001(part1of6)10.0points
A load of 800 kg is suspended as shown in the
following figure.
61
◦
38
◦
1
2
3
Calculate the tension in all three wires (that
is, the magnitude of the tension force exerted
by each of these wires.)
Begin with wire 1.
Use
g
= 9
.
8 m
/
s
2
.
Correct answer: 7840 N.
Explanation:
Wire 1 must exactly balance the downward
pull of gravity, so the tension must be
F
1
= (800 kg)(9
.
8 m
/
s
2
)
=
7840 N
.
002(part2of6)10.0points
Now calculate the tension in wire 2.
Correct answer: 3848
.
29 N.
Explanation:
This part may be trickier than it seems
at first.
You might assume that each of the
upper ropes contributes half of the tension in
the lower rope, but we don’t really know this.
We know two things: 1) since this situation
is an example of static equilibrium, the
x
components of the tension of the upper ropes
must be equal and opposite, and 2) their
y
components of tension must add to 7840 N.
We start by writing down an equation for the
x
components:
F
2
,x
=
F
3
,x
⇒
F
2
cos
θ
2
=
F
3
cos
θ
3
.
We can also write an equation for the
y
components:
F
2
,y
+
F
3
,y
=
F
1
⇒
F
2
sin
θ
2
+
F
3
sin
θ
3
=
F
1
.
Combining these two equations,
we can
eliminate
F
3
from the system to find that
F
2
=
F
1
sin 38
◦
+
cos 38
◦
cos 61
◦
sin 61
◦
=
3848
.
29 N
.
003(part3of6)10.0points
Now calculate the tension in wire 3.
Correct answer: 6255
.
01 N.
Explanation:
From the equations we deduced in part 2,
we know that
F
3
=
cos 38
◦
cos 61
◦
F
2
,
so we have
F
3
=
cos 38
◦
cos 61
◦
(3848
.
29 N)
=
6255
.
01 N
.
004(part4of6)10.0points
These wires are made of a material whose
value for Young’s modulus is 1
.
4
×
10
11
N
/
m
2
.
The diameter of the wires is 1
.
1 mm.
What
is the strain (fractional stretch) in each wire?
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview.
Sign up
to
access the rest of the document.
 Spring '11
 Antoniewicz
 Physics, Force, Correct Answer, Chauhan

Click to edit the document details