Version 017 – exam2 – markert – (58840)
1
This printout should have 14 questions.
Multiplechoice questions may continue on
the next column or page – fnd all choices
beFore answering.
001
10.0 points
Mary weighs 471 N and she walks down a
±ight oF stairs to a level 6
.
6 m below her
starting point.
What is the change in Mary’s potential en
ergy?
1. 2227.5
2. 2557.8
3. 2368.8
4. 3220.0
5. 3108.6
6. 3383.5
7. 2786.4
8. 3069.0
9. 2141.1
10. 1935.1
Correct answer:
−
3108
.
6 J.
Explanation:
We can let the initial potential energy be 0.
The change in potential energy is
Δ
U
=
U
f
−
U
i
=
mg
(
−
h
)
=
−
(471 N)(6
.
6 m)
=
−
3108
.
6 J
.
002
10.0 points
The amount oF work done by two boys who
apply 230 N oF Force in an unsuccessFul at
tempt to move a stalled car is
1.
230 N
·
m.
2.
230 N.
3.
460 N.
4.
460 N
·
m.
5.
0.
correct
Explanation:
W
=
F d
, so with an unsuccessFul attempt
to move the car, no work was done.
003
10.0 points
A car with mass 1212 kg, moving at 40 m
/
s,
strikes a(n) 2738 kg car at rest.
IF the two cars stick together, with what
speed do they move?
1. 11.493
2. 13.0147
3. 6.96477
4. 9.87273
5. 8.99133
6. 8.55566
7. 12.2734
8. 12.602
9. 13.4361
10. 6.51634
Correct answer: 12
.
2734 m
/
s.
Explanation:
Basic concepts
Momentum oF any object is
p
=
mv
The collision is inelastic, and by conservation
oF momentum,
p
before
=
p
after
m
1
v
o
+ 0 = (
m
1
+
m
2
)
v
f
v
f
=
m
1
v
o
(
m
1
+
m
2
)
004
10.0 points
²ive ramps lead From the ground to the second
±oor oF a workshop, as sketched below. All
fve ramps have the same height; ramps B,
C, D and E have the same length; ramp A is
longer than the other Four. You need to push
a heavy cart up to the second ±oor and you
may choose any one oF the fve ramps.
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2
A
B
C
D
E
Assuming no frictional forces on the cart,
which ramp would require you to do the least
work?
1.
Unable to determine without knowing the
exact proFles of ramps C, D or E.
2.
Ramp D.
3.
Same work for all Fve ramps.
correct
4.
Ramp E.
5.
Same work for ramps B, C, D or E; more
work for ramp A.
6.
Ramp C.
7.
Same work for the straight ramps A and
B; less work for ramps C, D, and E.
8.
Ramp B.
9.
Ramp A.
Explanation:
Let
h
be the height of the ramps. Since
there is no friction, we can use the work
energy theorem.
W
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 Fall '09
 BOCKNACK
 Organic chemistry, Force, Momentum, Potential Energy, mg T

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