lenoir (wml297) – homework 15 – Turner – (58220)
1
This
printout
should
have
12
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001
10.0 points
A hot rod of mass 1100 kg, starting from rest
reaches a speed of 150 m
/
s in only 26
.
1 s.
What is the average output power?
1.
0
.
00632184 MW
2.
0
.
948276 MW
3.
0
.
474138 MW
correct
4.
0
.
0181662 MW
5.
0
.
000121108 MW
Explanation:
The average output power is equal to the
kinetic energy acquired divided by the total
time, so
P
=
1
2
mv
2
t
=
(1100 kg) (150 m
/
s)
2
2 (26
.
1 s)
·
mW
10
6
W
= 0
.
474138 MW
002
10.0 points
A car with a mass of 1
.
09
×
10
3
kg starts from
rest and accelerates to a speed of 17.1 m/s in
18.1 s.
Assume that the force of resistance
remains constant at 310.4 N during this time.
What is the average power developed by
the car’s engine?
Correct answer: 11458
.
5 W.
Explanation:
Let :
m
= 1
.
09
×
10
3
kg
,
v
f
= 17
.
1 m
/
s
,
Δ
t
= 18
.
1 s
,
and
F
r
= 310
.
4 N
.
v
f
=
a
Δ
t
and Δ
x
=
1
2
a
(Δ
t
)
2
since
v
i
= 0
m/s, and
F
=
m a
+
F
r
, so
P
=
F
Δ
x
Δ
t
=
F
·
1
2
a
(Δ
t
)
2
Δ
t
=
F a
Δ
t
2
=
(
m a
+
F
r
)
v
f
2
=
parenleftBig
m
v
f
Δ
t
+
F
r
parenrightBig
·
v
f
2
=
bracketleftbigg
(1090 kg)(17
.
1 m
/
s)
18
.
1 s
+ 310
.
4 N
bracketrightbigg
×
17
.
1 m
/
s
2
=
11458
.
5 W
.
003
10.0 points
A car weighing 8800 N moves along a level
highway with a speed of 90 km
/
h. The power
of the engine at this speed is 67 kW.
The
car encounters a hill inclined at an angle of 6
◦
with respect to the horizontal.
If there is no change in the power of the
engine, and no change in the resistive forces
acting on the car, what is the new speed of
the car on the hill?
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 '10
 Turner
 Force, Kinetic Energy, Mass, Potential Energy, Correct Answer

Click to edit the document details