QQjectives for Chapter 10 - Energy. Work and SimPlg
Machines
Student Targets
403. I can identify kinetic energy as a function of velocity.
2. An object that has kinetic energy must be
a. moving
b. falling
c. pretty
d. elevated
e. at rest
A. Must be moving. It COULD be falling, but it MUST be moving.
3. Which gives the correct relationship for kinetic energy?
a. KE = mv
c. KE = mv/2
2
b. KE = mv2
d. KE = mv /2
D.
4. An object that has kinetic energy must have
(A) acceleration. B) a force applied to maintain it. C) momentum. D) none of the above
C momentum (if it has mass and velocity, it also has to have momentum.) Y, mY"> 0 then mv >0.
404. I can calculate gravitational potential energy' and kinetic energy.
5. What's the KE of a 100,000kg spaceship orbiting at 8,000m/s?
a)4x1013j
b)3.2x10'2j
c)4x10Bj
(0.5)(100,000kg)(8000m/s)2
= 3.2 x 1012J
406. I can identify that energy is transferred between different forms.
7. An arrow in a bow has 70 J of potential energy. Assuming no loss of energy due to heat or poor accounting
procedures, how much kinetic energy will the arrow have after its shot and traveling in air?
a.140J
b.70J
c.50J
d.35J
e.OJ
B. All of the energy would turn into kinetic energy. Work will produce energy. Energy can do
work.
1/
:= 6.1'-~
W02.l flON~"~ .e,ow =:
AU:
407. I can solve problems using conservation of mechanical energy.
-y.J
'10r :.
70r
408. I can apply the mathematical definition of work as the product of Force and
displacement.
10. How much net work is done by gravity on a rock that weighs 50 N that you carry horizontally across a 10
mroom?
a.500J
E. No Work
b.500W
c.10J
d.5J
~
~
~~
-.yr;.
j
0=96°
lO.5 ?()~:::O
:e-.
W=Fdcos 9
Since the weight acts at 270° and the displacement
downward cannot move a rock horizontally by itself.
is at 0° 9 is 90°.
cos 90° = O. Gravity acting
11. It takes a net work of 40 J to push a box of physics papers 4 meters across a floor. Assuming the push is in
the same direction as the box moved, what is the magnitude of the net force on the box of physics papers?
a. 4 N
b. 10 N
c. 40 N
d. 160 N
e. none of these
B.
W=Fdcos9
= F = Wid (cos 9) = 40J 14m cosoo = 10N
When there is an angle between the force and the displacement, W = F d cos9.
12. T/F
True. You have to take into account the angle between the force and the displacement.
forces won't cause a displacement.
Some
13. Clarice has a mass of 78 kg and climbs the schools stairs in 23.0 seconds. The school stairwell contains 41
stairs that are 18 em tall each. How much work against gravity did Clarice do climbing up the stairs?
a. 5641 J
b. 576 J
c.564127J
d. 245 J
e. 764 J
a.
W=Fd(cos
9) = mgd (cosO) = (78kg)(9.80m/s2)(41stairs)(0.18m/stair)
409. I can identify situations
of net positive work, negative
= 5641J
work, zero work.
14. When friction slows down a ball, friction is doing:
a) Positive Work
b) Negative work
c zero work
b) Work would be negative. Friction always opposes
displacement is 180°. The cos 180°= -1. Work from friction
motion, so the angle between force and
is negative.
410. I can identify work as a change in energy.
15. The amount of potential energy possessed by an elevated object is equal to
A) the
B) the
C) the
D) the
E) the
distance it is lifted.
work done in lifting it.
force needed to lift it.
value of the acceleration due to gravity.
power used to lift it.
B) Energy comes from work.
OPRF Physics Custom
The work you do turns into energy.
Objectives
Note: any objectives involving calculation of one variable imply the calculation of any other variable in
the equation. depending on the given information.
10/11.1
16.
Calculate power.
How much power is required to do 100 J of work on a 35 kg object in 2 seconds?
a. 17.5 W
b. 3500 W
c. 200 W
d. 50 W
e. 100 W
d. P =
Wit = 100J/2s = SOW
17. Power equals work multiplied by time.
a. True
b. False
False.
Power = work divided
by time.
10.4 State SI units for work, energy,
spring constant,
and power.
21. The unit of energy is the watt.
a. True
b. False
b. False,
The unit is the joule.
22. The unit of power is the watt.
a. True
b. False
A. True:
1J/1s = 1W
23. The unit of work is the Joule.
a. True
b. False
A.
True.
11.5 Calculate answers for hypothetical energy scenarios
you double the velocity, what happens to the energy. etc)
using the idea of proportionality.
(e.g .. if
24. If you lift two loads of equal weight up one story, how much work do you do compared to lifting just one
load up one story?
A) Four times as much 8) One quarter as much C) Twice as much 0) One half as much E) The same
amount
This depends on the interpretation.
If you say you carry two loads up one flight vs. carrying
two loads at once up the stairs, the answer is E. W=Fd cos 8.
the
Another way students interpreted the question that each load was the same weight. If each load
is the same weight, taking two loads is double the force. In this case, two loads would be twice
the work. The answer would be C.
25. If Nellie Newton pushes an object with three times the force for twice the distance, she does
A) three times the work. 8) six times the work. C) four times the work. 0) the same work.
F2 = 3F,
d2=2d,
W2=F2d2={3F,)(2d,)
= 6W, Answer:
(B)
26. How much farther will a car traveling at 200 km/s skid than the same car traveling at 100 km/s?
r;,
'w'~('.",tt.",,~AY£
••'
A) The same distance 8) Five times as far C) Half as far 0) Four times as far E) Twice as far ...0) There is four times the energy, so the skid would be four times the distance.
27. If a student pushes an object with twice the force for twice the distance, she does
a. the same work
b. twice the work
c. four times the work d. eight times the work
F2 = 2F,
d2=2d,
W2=F2d2={2F,)(2d,)
= 4W, Answer:
c.
28. How much MORE kinetic energy will a car traveling at 100 km/hr have then the same car traveling at 50
km/hr?
a. five times as much b. four times as much c. twice as much
d. the same e. half as much
b. four times KE1
= % m~ = % m (50m/s)2 = 1250m
KE2
= % m (100m/s)2
= 5000m
Mechanical advantage
Calculate the mechanical advantage of a lever that moves a 12.000N object O.20m when a person
applies a force of 91ON over a distance of 3.00m. Calculate the ideal mechanical advantage for the
system. Calculate the efficiency of the system.
=
=
=
=
=
=
MA F,/F. 12,000N/910N
13
IMA deld, 3.00m/0.20m
15
e MAtiMA x 100 13/15 x 100
=
=
= 88%
A student takes the following data for a spring. Find the work done on the spring and the spring
constant.
Displacement
0.0
0.0
0.3
0.5
137.5
275.0
0.8
1.0
412.5
550.0
1.3
1.5
687.5
1.8
2.0
2.3
2.5
2.8
3.0
Slope= spring constant = 550N/m
Force
825.0
962.5
1100.0
1237.5
1375.0
1512.5
1650.0
Slope = (y,-y,)/(x,-x,)
= (1375N - 550N)/(2.5m -l.Om)
= 550 N/m
W = area under graph = )I, bh =)1,(3.0m)(1650N) 2475J
Force vs. Displacement
3000.0
2500.0
2000.0
1500.0
1000.0
500.0
0.0
0.0
1.0
k = 550N/m
W
= % (J.Om)(1650N) = 2475J
2.0
3.0
4.0
5.0
6.0
A student takes the following data for a spring. Find the work done on the spring and the spring
constant.
Force
Displacement
0.0
0.0
0.3
137.5
0.5
275.0
0.8
412.5
1.0
550.0
1.3
687.5
1.5
1.8
2.0
825.0
1100.0
2.3
1237.5
2.5
2.8
1375.0
3.0
1650.0
962.5
1512.5
Work Done by.a Constant Force
Choose from the following list:
2) Two men, Joel and Jerry, push against a wall. Jerry stops after 10 min, while Joel is able to push
for 5.0 min longer. Compare the work they do.
A) Joel does 75% more work than Jerry.
~
B) Joel does 50% more work than Jerry.1J
C.( ~
C) Je(~
0
more work than Joel.
<:0) Neither of them do an wor.
=--f
Answer: 0
Diff 2
3) You lift a 50. N physics book up in the air a distance of 1 m, at a constant velocity of 0.5 m/s. The
work done by gravity is
A) +50 J.
)-
J.
-50 J
~
c9=-ltJO'
roo
E) +100 J
Answer: C
Diff: 2
~J,
W::
F.J= tJ
C()~B
::{PN )l f J~Of.{86~
'{-50!)
ttl
4) Matthew pulls his little sister Sarah in a sled on an icy surface (assume no friction), with a force of
60.0 newtons at an angle of 37.0° upward from the horizontal. If he pulls her a distance of 12.0 m, the
work he does is
A) 0.333 kJ
~!W
E) 185 J
Answer: C
Diff: 2
F=-ftjAJ
9-=-376
:: l6NYJ2"')~3:1:J
d =-(2.M.
/.~
-?
( ~:57rJ~
q
7) An auto is coasting on a level road. It weighs 10. kN. How much work is done by gravity as it
moves horizontally 150. meters?
Answer: zero (displacement is perpendicular to the force)
Diff: 2
8) If there is no motion, can work be done on a system?
A) yes, provided an outside force is applied
B) yes, since motion is only relative
.9J1n-since.a.sy.sl
'c is not movin has no kinetic energy
~ecause
of the way work is defined
\
r
w -I-.J
Answer: D
Diff:1
Choose from the following list:
(a) friction
(b) J/s
(c) dyne.cm
(d) N-m
(e) 550 ft.lb/s
(f) mgy
(g) 1/2 mv2
(h) dimensionless
(i) N/m
U) 3.6 MJ
(k) ft.lb
(I) -kx
(m) weight
(n) ft.lb/s
iJ - 1
9) Match joule to one of the choices above.
AnswE>N-~
Diff: 1
_
~
F(N)
5
o
5
x (m)
10
6) The force that a squirrel exerts on a nut it has found is observed over a 10. second interval, as
shown on the graph above. How much work did the squirrel do during that 10. s?
b.l~:~
25.J
.
E) zero
"OeL
e
AW<
i b~ Y.(jCW) w)
~fJ
:::2~3
-
e
_
Answer: C
Diff: 2
7) The force that a squirrel exerts on a nut it has found is observed over a 10. second interval, as
shown on the graph above. What was the average power exerted by the squirrel?
A) zero
B) 1.3 W
~
D)L:21iiI
E) 5.0 W
Answer: C
Diff: 2
9) Consider a 0.002 gram mass hung from a spring. When an additional 15. kg is added, the
equilibrium position changes by 20. cm.
(a) What is the spring constant?
(b) How much work is done on the spring? Difficult - Draw graph
(c) If 30. kg are added, by how much will the equilibrium position change?
Answer: (a) 0.74 x 103 N/m
(b) 15. J
(c) 40. cm
Diff:3
11) When you lift a 12. ounce (3N) beverage can from the table top to your mouth, you do
approximately how much work?
A) 1 Calorie
d.=tJ/
B) 1 Wall
C)1
1 Joule
COJ
erg
F::-3N
3M.
VI:: f.J e
:: @j.J'fE.3JY\ks.O)
Answer: 0
Oiff:2
~6fiJ
13) You throw a ball straight up. Compare the sign of the work done by gravity w .
with the sign of the work done by gravity while it goes dow~
A.) Work up is -, and the work down is -.
L~
B) Work up is +, and the work down is +.
it .1
..gwor~
up
IS -,
l5)wort< Up Is +,
r
a~;1c/~::O~
t::K
crown IS +.
down IS-,
")
t
~"
I
a
Answer: C
Oiff:2
e ~ISo"
e =0'
Work Done by a Variable Force
1) A 10. kg mass, hung onto a spring, causes the spring to stretch 2.0 cm. The spring constant is
A 5.0 N/cm
B 49 N/cm
It:
~
C) 0,20 N cm
0) 20. N/m
2.'1",::6,021'1'\
E) 0.0020 N/cm
~~161(~F;
J~
Answer' B
Oiff:2 .
@
J:
r:--
F
-;}
'f
J~
([OII'j~.8~"L):: 18N
_ o0I-J
la
-
---
-
0, 02.~1-
5) The~r
UQ
l{'DO NJ/II
r the curve, on a Force vs. position (F-x) graph, represents
work.
I
B)-e . lency.
F Ofll,cv" I{<SP M.e.n.r
C) kinetic energy.
0) power.
E) friction.
Answer: A
Oiff 1
Ia",
I
dr-
l(71c
If)
8) The resultant force you exert while pressing a key on the keyboard of your new computer, for a
1.0-s period, is plaited on the graph, shown.
x(m)
-5
How m~ch
zero
did you do during this 1-s interval?
.J
C) -25. J
D) 12.5 J
E) 22. J
Answer: A
Diff: 2
10) Daisy
(a)
(b)
(c)
'G.:' ffI!J.-QO/~.e~:J~
9!1.!
d
raises 10.kgto a heightof2.5 meters in 2.0 seconds.
How much work did she do?
How much power was expended?
=
"I.
If she raises it in 1.0s rather than 2.0s, how do the work and power change?
z.S-
w,-::W •.
-<It'
2.
(b,2 I
7..0}.
11) Consider a plot of the applied force (F) vs,
of the curve would be
ISP
uN
M
2-.S''''_~OJ()j
-c L '-f S
3 vJ
":Sil\.Le
0~
jl
'r;
~..
-
2.P\~Pt
<
t- .. 2,0.,<
,\rJ--FJ..fJco16
p~V ,,'Z-'tS-r
Answer: (a) 0.25 kJ
(b) 0.13 kW
(c) same work but power doubles
Diff:3
'i 7
e
_
~
4t:{ Pt("~
acement (x) for an ideal elastic spring. The slope
~::::
~g~:~fo~~~~~a~pring
constant.
C) the acceleration of gravity.
D) the reciprocal of the acceleration of gravity.
Answer: A
Diff:2
The Work-Energy
Theorem:
Kinetic Energy
1) A driver, traveling at 22. mis, slows down her 1500. kg car to stop for a red light. What work is
done by the friction force against the wheels"\[. ..
-VI :.u1J "Of ~ 0 M '" l~d'1
Ak e
5
Answer: 3.6 x 10 Joules
Diff:2
'I,.,r- Kef - t: G l . " 1.
/'II. 1Y""
z.
I-
1
--z /V1V,
.~
G lIS-OOk~(O"t%-[~i~l~l2"r.J] (3 61
60u ~
Choose from the following list:
(a)
(b)
(c)
(d)
(e)
(f)
friction
J/s
dyne-cm
N.m
550 ft.lb/s
mv2
(h
ens ion less
(i) N/m
OJ 3.6 MJ
(k) ft-Ib
(I) -kx
(m) weight
(n) ft-Ib/s
2) Match kinetic energy to one of choices above.
2
Answer: (g) 1/2 mv
Oiff: 1
3) The work energy theorem says
A) the net work done is equal to the initial kinetic energy less the final energy.
B) the net work done plus the final kinetic energy is the initial kinetic energy.
the ne w
one-ptus"tl1eTr'iITlalKmetlc energy IS e Inal me ICener
0) the net wor
1m la kinetic energy IS e Ina me IC energy.
E) final kinetic energy plus the net work done is the initial kinetic energy.
\r "~It. 6
Answer: C
o iff: 2
' " VI =: j( C f - K C(
V+ K(,~ ~ff
<=-
4) Car J moves twice as fast as car K, and car J has ha fthe-mass-of-ca-rK
lJ
J, compared to car K is
~
r
= 2lJ K.
i'v'I
- l M
~-'Z.-K.
~
g)42et~a1~e.
E) 1 to 2.
({)
~
MJl.)J
~
':
~G~
_
\(
!(~rt\,<-}..2iJ~)2_
.!..I
-i--
\
-2..
\'t\t
The kinetic energy of car
1JL
Answer: B
Oiff: 2
,
M <.. V'"
<-
B
5) If both the mass and the velocity of a ball are tripled, the kinetic energy is increased by a factor
of
31\, '; 1\\....
A) 18.
Su, =
\)2
B) 81.
C) 6.
&!Y
Answer: E
Oiff: 2
~'
iQrr.,'j)"roJL
t
,
(\'I, 7), ">.
6) Is more work required to increase a car's speed from rest to 30 mph, or from 50 mph to 60 mph?
1\
Answer: 50 to 60 mph
Oiff:2
1-\
~t:: ..:.
M 1) ~
2..
t-
7) Kinetic energy is proportional to speed.
Answer: FALSE
Oiff: 1
~ W\
iJ"'\ V 2..
-
IT IS-pl'l>par-'hIOMiJ;
IIt-o~o.,.~.M.••.1 \-llS
-..!.
~
M -V' 1-
("
[V~\.,- V,,'j
1
30
01. :.
------~-
~6qL_g)1-
too :~~
~ liDO i~")
- -
9) A truck weighs twice as much as a c~~
g at twice the speed of the car. Which
statement is true about the truck's kinetic energy (KE) compared to that of the car?
A) The truck has 4 times the KE of the car.
tt. T'_- 2./VI."
1/ .". -1
l.
B) All that can be said is that the truck has more KE.
..., I
2..
I'U - -uM 1)
C The truck has twice t
r.
V-r ':- Vc..
0) The tru
_s times the KE of the
r.
1"..
1I
Z
E) The truck has
times the KE of the car.
I
fl\r 'U
2Ll.
J2
Answer: 0
Oiff:2
Choose from the following list:
(a) friction
(b) J/s
(c) dyne-cm
(d) N-m
(e) 550 ft.lb/s
(f) mgy
(g) 1/2 mv2
h . ensionless
i) N/m
J
(k) ft-Ib
(I) -kx
(m) weight
(n) ft-Ib/s
3) Match spring constant to one of the choices above.
Answer: (i) N/m
Oiff: 1
la:, Ji
~:
J.f,.
JC?vc..J
r r..(2 •.•..
r\.1);;-"
'7
Me.. V", L~
~
t) ~c..
V';?-
(I1l;.
t
8) On the accompanying diagram of a pendulum, at
wha~
the kinetic energy maximum?
~
I(~~~ M -U 1..
C) C
Answer: A
Diff: 2
-
13) On a plot of F vs. x, what represents the work done by the force F?
A) the slope of the curve
B
en th a
C the
under the curve
D) the pro
aXlmum force times the maximum x
E) the maximum F times minimum x
Answer: C
Diff: 2
9) A "machine" multiplies (increases)
A) time.
B) energy.
C
f('
--::::.-
re
tJbth~'3CalA ~vw"\~\J
Answer: D
Diff: 1
I.IScrl
Ot'
eJ.t~
J or powtV.
10) You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level
road. If you had been traveling twice as fast, what distance would the car have skidded, under the
same conditions?
\
2c.Ai
auld have skidde 4tiilies fartheC)
":;'
1)
-8) IrwouICDtave-skiddecr~5
Far.
eC) It would have skidded.J2 times farther.
T
D) It is impossible to tell from the information given.
'IVfN~
M
K
\"
11 E :::
Answer: A
Diff: 2
I"'n
I : ~~
2...1), : V~ :
L.
14) A 4-kg mass moving with speed 2 mIs, and a 2-kg mass moving with a speed of 4 mIs, are gliding
over a horizontal frictionless surface. Both objects encounter the same horizontal force, which directly
opposes their motion, and are brought to rest by it. Which statement correctly describes the situation?
A) Both masses travel the same distance before stopping.
B) The 2-kg mass travels twice as far as the 4-kg mass before stopping.
C) The 2-kg mass travels farther, but not necessarily twice as far.
0) The 4-kg mass travels twice as far as the 2-kg mass before stopping.
E) The 4-kg mass loses more kinetic energy than the 2-kg mass.
Answer: B
Oiff: 2
23) A container of water is lifted vertically 3.0~en
weight is 30. N, how much work was done? u.lil
A)0.18kJ
B) 45 J
0
90~
::>
t
&=0" oil
.i
I
No work was done.
. -O.J~ kJ
-
~
Answer: 0
Oiff2
Power
retur
F:~1I.9.,
to its original position. If the total
tJw;J
J
..,
d
"f.
•.•
I pUJI'
&:(e6~
V ~WoP 'lJ;_ ~ ~D",£l;;{'o;O~+~)~) ••,,~
-:: 9 OJ 4 t 90 J~(
(1)
Choose from the following list:
(a) friction
(b) J/s
(c) dyne-cm
(d) N-m
(e) 550 ft-Ib/s
(f) mgy
9)1/2
2
Imensionle
~(i)
m
U) 3.6 MJ
(k) ft-Ib
(I) -kx
(m) weight
(n) ft-Ib/s
2) Match efficiency to one of the choices above.
Answer: (h) dimensionless
Oiff: 1
3) Match watt to one of the choices above.
Answer: (b) J/s
Oiff: 1
J~fvW\-doll
:.- &t'rM~
leu Lit f-tt,,)
~ ~'4lf leJ..S
e:: :;".
L I CR-~w)
JiMe •..~lblt'e-Si(va 1"-t0
7) Compared to yesterday, you did 3 times the work in one-third the time. To do so, your power
output must have been
"7
A) the same as yesterday's power output.
V L'2
I
B) one-third of yesterday's power output.
IJ\ IC) 3 times yesterday's ower output.
~ 1
~.:,
U-Yl
.9.
s yes er ay sower ou
f\
~
-
-VI r 3 \J
A ".!-
r
At
D- .J!-
r-
t'T
r ':!£.-
C) '"",,me, y",'ecay', POW"o"P'1.
Answer:
f.
0
0
'~h
,
6,t
Q
I
j
.<\
'::
V.
At
Diff: 2
q~.
~ W,
~
At
l\
I
::-
7
,
13) A roofer lifts supplies a height of 20. m with a hand-operated winch. How long would it take him to
lift a 200. kg load, if the winch has an efficiency of 90%, and the rate at which the winch can do work
is600W?
J.=20",
Answer: 73. seconds
Diff: 2 V;:: V.
I.
if
p= '0000
P=-YJ.\:.
"T
••
'{\J •
F<~= fcx>t:))U.&I'lI.l') = 1.',80AJ e=-'16;"
r\\1't
1J,.
TriP. "" ~\JJ
4. t.?
-.
t t-~~F;oL
""
M.-::200~
f
(.
• -
.~
~
-
e
0 '
~t~fJb",) ~
\;;~
~~v
" I"
..1-_
4
15) Water flows over a waterfall 20.mn'rgh, at the rate of 4.0 x 10 kg/s. If this water powers an
electric generator with a 40% efficiency, how many watts_of electric power can be supplied?
et ~ WM, ~~
t
VJ.~efJJ,~poura~~
Answer: 3.1 MW
Diff:2
'-t. 0 X/t> ~Kj/c
p", J[
t
~ ~~
1,J,n
F~
"'::1
6,0)7Gl rtff Wb~,\
-=-
3'1 ~),
e.W,,, :: @,({Jf!i.fJ{/OS'0)f<OiJG1;(oi$~r)
S
_
o¥.y'
tv;;
18) Lisa runs up 4 f1ifftlts of stairs in 22. ~econds. She weigh~510. Newtons. If each fllgtlrrises
310.cm:
F:~\OI\J
of •• !J1O~\J.l~I' ~~\I.l..!!:J.-\
/2. II
(a) What was her work?
'=- 2..2.~
'1''J~ 'j ~ loacI 0\.1
(b) What average power (watts) was required during the 22. s? .•. / _ I
t.
J :: ,
W
Answer: (a) 6.32 kJ
(b) 287. watts
Diff:3
=-
"&-!. ~
FJ cO,($-
(a) ""(5(OAJQZ,lfM
Lb)
p.:;r..
<3: O.
::
t :32.05
= 2.8 7 W
b~
19) A cyclist does work at the rate of 500.w while riding. With how much averag~*~rizonta
does the wheel push when she is traveling at 10. m/s?
Answer: 50. N
Diff:2
P :: f -0
f-- J:- _- S"O
-u
I
P
F;; 7.
:-SZV 'oJ
A~swer: 3.7 kW
Dlff: 2
'" 2{)
e '.,]
\r/:"
/ ~ "'/~
Iv.
c _
'-j -
w> \Tr (
-
'.'¥-t
,.Ir /\ I-
(,J.
.:>
rgy when he runs up a
~
_
Mj @--''jfl.8~'J.:Jb8'';6=0'
t "-t:> 0 S
I
C
e..
M:: (PO
r,J ~;::IJ
e
cJlwJ
~.::.':!£.::
(O'i/
.::. !.S
I<,j',%3
21) Assuming muscles are 20% efficient, at what rate is a 60. kg boy using e
flight of stairs 10.m high, in 8.0 s?
V
'Sb€;fJ
0/11
6,~
()
Difficult
8) A brick and a pebble fall from the roof of an apartment building under construction. At some point
the brick is moving at a speed of 3.0 mls and the pebble's speed is 5.0 m/s. If both objects have the
same kin .
what is the ratio of the brick's mass to the rock's mass?
A 25 to 9.0
B . 0 .
C) 5.0 to 3.0
D) 12.5 to 3.0
E) 12.5 to 4.5
Answer: A
Diff: 2
Chapter 11 Review
NOTE: The following question(s) refer(s) to the Cyclone, the famous roller coaster ride at Coney
Island, shown in the sketch. Assume no friction.
SOm
_.1_
p
R
5) If the roller coaster leaves point Q from rest, how fast is it traveling at point R?
~)31m/s/S
0) 0.49 kSm/s
E)51m/s
Answer: B
Oiff: 2
1..,:
Kt; 1'1.111\./'
PC:~k.
1Jt:O"~
'>0'\
/I\~k:t
~f=-OM
i
1-I~V'l.:
V •.?
r .
~= ""
Q ",
-=
IV1V;"
•
V, ' -
i2s~,t 1): -
.m
pf.,,: ~ l
kf
-.J
E) 1.4 km
rv\G. ~ :
;It Vf
1
';> '\-
z-~-~-:j-y-.!\-i'-:-)1O-.tJ~313 ••1
.
Ij
=- 1)/
: Vf
the exact top of its trajectory, its
/.,
!lfOI
=- \ YO J
D)0.12km
Answer: B
Oiff: 2
2j
IVI"
(0 N
\'<\<\:
+~
-/1.,
I
11) A toy rocket, weighing 10. N, blasts off from ground level.
energy is 140.J. To what vertical height does it rise?
A 1.4m
CB) 14.m
h,
fvt~
j ~. ..,.
7 \.
,
-.J
2jk,,
PCLr/<C-=PCrll:Cr-
p~
~
18) A leaf falls from a tree. Compare its Kinetic,energy KE to its potential energy PE.
~e>A KE increases, and PE ecreases
tJo "'0
B)
ecreas,
n
Increases. --.. . ~
f 1£
00
'JC:> C) KE deCreases, and PE decreases.
/
.'
y~s Ii\) 0) KE increases, and PE increases.'
lJo Nt}
E) KE and PE remain constant.
~
(r~
'J'!"
Answer: A
Oiff:1
20) Is it possible for a system to have negative potential energy?
}-Yes--.a.sJ.ong.8sh total ener ~os'
.
Yes, since the choice of the zero of potential energy is arbitrary.
C) No, because
ISwou CI11ave"1'iopliyslca meaning.
0) No, because the kinetic energy of a system must equal its potential energy.
Answer: B
Oiff: 2
fR..oM,
Gr
r:.1\€~
b: 1((J(:1~
~~Id(?
t
~(!l'" I
CKooSt:
av-~
q
+h.e. raul:':!J
'2.evo
I ~
0 t-<
lel.el. :. P t = ":5h
eel-I'\,
'~i:~
NOTE: The following question(s) refer(s) to the Cyclone, the famous roller coaster ride at Coney
Island, shown in the sketch. Assume no friction.
SOm
0""
_1-_
--
P
R
16) How fast must the coaster be moving at P in order to coast to a stop at Q?
A) 9.8 m/s
l ml
~ . mI s
0) 0.49 km/s
E) 0.98 km/s
KB+P~
=
"
1L/r\t) '...JII."
1 t 1.'\111
I
l.-
"i- V,
j
t
l
L
UfrP=
L
I
k~o .... "'...""
~I -""/
Vf
k
I
-= Z.Vf
;
= ~ ,41 V 2.
-u _ ?
f
lM't) II! Mj ~ r.,
'"
P ( •. tY1j t.. KC
~,
1f
-",
Ij
"'W"
V~ = ( 1J1'TL5hl-Z. I,
Answer: B
Oiff: 2
Y
'"
.1)'
t'i~
r:
hi,
-enp.)
t-.
t L2cz8"6tiOI\)
~ I ) 3.-;-"'ZJ
21) King Kong falls from the top of the Empire State Building, t oug the air (air friction is present), to
the ground below. How does his kinetic energy (KE) just before striking the ground compare to his
potential energy (PE) at the top of the building?
p~,t I< c,'
IgE.f
<:;
-=:
f't:l
f f7 f
I
K.. [f
-I ~,
SI'fI,(~
,h'<I '"
•.
Wf"'(}IO":>
0
Answer: C
Oiff:2
22) A skier, of mass 60. kg, pushes off the top of a hill with an initial speed of 4.0 m/s. How fast will
she be moving after droPPi~~ 10.m inti'eleVa~i~n? (ig~~e friction) M."
A)0.20km/s
l~)~~
tl1S1
)
. m/s
I
O)0.15km/s
E)49.m/s
Answer: B
Diff:2
rl"..j'
+
tf\4lv
't-! (>\ VI.",
z-,
J"
I
'(1;,.,,,:: rGjlt
I-'vf
j k.!.
f r
M..
I
Mj~,-+;'''''1..,,1..
{ 2..jhl
t
1), L
"Z.
M. V,
-th ~ L{.O % f.... ~ 10.", h ~o
f
PI!~M.j""" 1<'~:i.<{Vl
7-
(
-IV\~~~"
I
j k \t !. 'O,! - 3 ~t
I
bok-j
i MV,'l.
1
:: L'V,.
2-
-2.J~f -=--Vf
2(9.71"l>i/~ +-
&"4)1 _[2[fleMIs0(O,,)
=@lil
23) A container of water is lifted vertically 3.0 m, then returned to its original position. If the total
weight is 30. N, how much work was done?
~l
~;~
kJ
C
v-
[lPf;"
It" j, 0"" A.: ~c.J Af" (J
M~J, /Jp}.J'jo"'jJ _ ;gaAJp~5J
"j :: 3Ci tJ
Mj ~f -
M
"1
p
-a r
EEl
J
ill) No work was done.
E) .
Answer: D
Diff 2
24) A 1.0 kg flashlight falls to the floor. At the point during its fall when it is 0.70 m above the floor, its
potential energy exactly equals its kinetic energy. How fast is it moving?
M=-I.~
j ~.8?;~
v=w
~ f2<7.8'Ys')!,7~
C ,7W
Pf=~~
~r={ ,,",<J'-
k "0,70",
pe ~It. r;
M.j ~:: ){
Answer: A
Diff 2
.2..j~~
3
to\. 7J
z.
V/..
r
You have a 12.5g popper that is 1.0cm tall when turned inside out. It reaches 1.00m at the top of its
trajectory.
M -: /2'(j
Assume no friction.
('k;;
O,oI2r-k
h. =..
d= (00(;;,)
!,C0M.
A. What type of energy does the popper have whJ'n It is barely off ~e table?
Pl
B. What is the potential energy at the top of its arc?
C. What is the kinetic energy at the top of its trajectory?
F. What is the force of the popper on the table?
a:.) w=4r..e.::if)
().I2-z..~J
l
'-t
f-
~
-t M-V
TO
-..)
K C=Ptr &.612.ntj/J,Ji!J/ •.~
() t
~)
l
'" "'~/...
1- 0, /22.S'"sl
,11--(,j
-
r;]{.. ': 0, 1~2S1
d.
0
-
,O{~
j/2.tS'iJ'
1
1. Which type of energy is associated with a body's height above the ground?
a. thermal energy
b. elastic otential ener
'"
I
c. gravitational potential energy
t\
. r s energy
__
r e:....: ~
Answer: C
10
1(( .'" p~. r I< c:
(
D. What is the kinetic energy when the popper is barely off the table?
E. What is the work done by the popper?
Answer: A. kinetic
B. 0.1225J
C. 0 J
D. 0.1225J
E. 0.1225J
F. 12.25N
t
~ 0,0
(c. J KCf
~()b
fop J orc-
.!.Iofs
OJ) K t::-:Pt i =- 0 tv
I
$j
3. Which gives the correct relationship for kinetic energy?
a. KE = mv
z
b. KE = m-l
tC= ~
MVZ.
-=
~
c. KE = mv/2
or:
Z
RE_= m\?9
Answer: D
4. An object that has kinetic energy must have
A) acceleration.
B
p lied to maintain it.
) momentum.
ne of the above
\
Z
MV<
~ef'
Answer: C
>6
---
E>o ?b
404. I can calculate gravitational potential energy' and kinetic energy.
5. What's the KE of a 100,000kg spaceship orbiting at a,OOOm/s?
a
1013
12
1)~-I"2
b) 3.2 x 0 J
"VM:V "" -z. I DO00"1
x 0 J
'
IC}
:z
Answer: B
. '(8
~.l
~J,()oO M/c,.J
C:~3,2..xI(~/I)
405. I can identify an isolated system and analyze it.
6. A gymnast falls from a height onto a trampoline. For a moment on the trampoline, both the
gymnast's kinetic energy and gravitational potential energy are zero. How is most of the gymnast's
mechanical energy stored for that moment?
a. Rest energy
b. C
icaL
tial energy
c. Elastic potential ener
!-efle
\~
5u..T
Answer: C (in the springs of the trampoline)
406. I can identify that energy is transferred between different forms.
7. An arrow in a bow has 70 J of potential energy. Assuming no loss of energy due to heat or poor accounting
procedures, how much kinetic energy will the arrow have after its shot and traveling in air?
~
:+
d. 35 J
e. 0 J
Answer: B
8. If I drop a rock from a cliff it starts off being primarily
mainly___
and right before striking the ground it is
p[
d
J'\~~
a. Kinetic; Gravitational potential
cr:rnv1tatlmtaPirtenlia
I; Klnet':S1
.
i aVllauona;
lasbc
Answer: B
Mc.,K_
407. I can solve problems using conservation of mechanical energy.
9. As a pendulum swings back and forth.
A) at the end points of its swing, its energy is all potential~e.>
B) kinetic energy is transformed into potential energy. ~[5
C) at the lowest part of its swing, it has maximum energy. y C)
D)
Atiat-energ' transformed into kinetic energy. Y"5
all of the above
C. •
1< C.
Answer: E
408. I can apply the mathematical definition of work as the product of Force and displacement.
409. I can identify situations of net positive work. negative work, zero work.
(9
/0" (;,c)(
C~
Answer: B
QV\
=
/8()"
I&J~==@
410. I can identify work as a change in energy.
15. The amount of potential energy possessed by an elevated object is equal to
..the.rlistaoo . . lifted.
B) the work done in lifting I .
-r;.,r.:= 4 Pc
~oc~~I~~ation
due to gravity.
-VI-- r: J ~~) J ~
I
~; :~: ~~~:ro~;:~
I.
Answer: C
OPRF Physics Custom Objectives
Note: any objectives involving calculation of one variable imply the calculation of any other variable in
the equation, depending on the given information.
11.1 Calculate power.
11.2 Apply conservation of energy to various problems. taking non-conservative
18. En~sforms
forces into account.
from one form to another with no net loss or gain if it is a closed isolated system.
(~
~~
.
~
"
€l-\.. tll'e-
S 4 S rC:'vV\.
J
Answer: T (net for the entire system)
\i
(Cl->A. ~V'd..II'-I
f'e
V'
"-tl-e !::sst-eM, be..L.r
I
hfCfl,J..JU"I +£Apa~ '" I '/-hI'"
I\.ot
be
1oY-
19. The American Falcon roller coaster has a mass of 2000 kg and its tallest hill, the first hill, is 24 meters
above the ground. The coaster races down the first hill then up to the top of the second hill, which is 3 meters
above the ground. Assuming that we lose no kinetic en~y.Jo friction, how fast is the American Falcon going at
the top of this second hill?
C .4Ml<i~
f>\d ~. "11"\11" -= "'j L -I J f\ V l..
of ~ ~
J '
,
f
Z
f
9
8
I
a..
ms
I
b. 21.7 m/s
C--''''qh,
L'i"
j l., 4.!.t. V I - JQ hf ~ .!Z V I z
,)
I...)
Is
c..7 7 m
f\(:- I"\V'
I • >
r---__
p
~
~..20.3m!0
Answer: E. 20.3 m/s
M,'
"I.J~
"Z
Pc.,tU.:f>(ftKCf
k r Ji,'''V/
i\~
1).=0-(,
~,,~lyr
;
fl1
V/
-VI' ,
j
1
2jl;tV,.
-2.$l..,
_
.
Vf
f [i.&.81,.XZ.~..) tV ~J-[z(~,tr,~j"ilf
20,3 ~
:l fbi'
11.3 State and/or recognize conditions of validity for conservation of mechanical energy of a system
(must know definition of a closed system).
Answer: A
11.4 State SI units for work. energy. spring constant. and power.
11.5 Calculate answers for hypothetical energy scenarios using the idea of proportionality. (e.g .. if
you double the velocity. what happens to the energy. etc)
These problems are more difficult. Good practice, if you know your
stuff.
14) A 4-kg mass moving with speed 2 mIs, and a 2-kg mass moving with a speed of 4 mIs, are gliding
over a horizontal frictionless surface. Both objects encounter the same horizontal force, which directly
opposes their motion, and are brought to rest by it. Which statement correctly describes the situation?
Both-masses.travelthe.same
dis.tance before ~pping.
B) The 2-kg mass travels twice as far as the 4-kg mass before stoppi.!J.97
~ C ne2':'Rg mass travelsrartller, but Ilorrrecessarily-twice-as"far.--D) The 4-kg mass travels twice as far as the 2-kg mass before stopping.
E) The 4-kg mass loses more kinetic energy than the 2-kg mass.
Answer: B
Dirt: 2
'vJ : 8.. tt -= FJ
KC, ' t & kj)(2 "S ~8j
I(~: ~(L~)(~",S'16J
r,ct~bJ
r. ),"
\'YIL.~ 2 tj
V,: ~ 2"'~ Vr ~ 0"'6
-v" = 2 •.•
~
f,:r:
J
(£ f
leiI- = 2),
M,: L(~
7
NOTE: The following question(s) refer(s) to the Cyclone, the famous roller coaster ride at Coney
Island, shown in the sketch. Assume no friction.
s
SOm
_1-_
p
R
.:~---
15) If the roller coaster leaves point Q from rest, what is its speed at point S (at the top of the 25. m
peak) compared to its speed at point R?
--
A) zero
B) 1/,12
C) ,12
0)2
E)4
)
Answer: B
Oiff: 2
19) A 30. N stone is dropped from a height of 10. m, and strikes the ground with a velocity of 13.m/s.
pC j' t Kg, ". P r 9 f 1
What average force of air friction acts on it as it falls?
v~:O~I
~ lJ):I /3",/(
.)
,\
A)7.2N
B) 2.9 N
N '::
.3D~
C) 1.2 ~
'\-2)4 1
-..l
]
""i.::
E)0.13KN
I
\
j""
1'\
\
t
\DM
1.
1
-=
-.J
~
.:...M7)....
2.
(
l
l
M V,
\
M.11~ t
\
f
i
£ MV,' -':j~-~
MV,2
I
r 4'
fJ
1.."-
- ~ "" - 'i.. llA "V(
i= A
-::
~ ' t::f
=
'Fr
J
Answer: 0
Oiff: 2
[00jj'ilb~4&-~D~itYO~-~~~,,~-
~c.:'~~
10M
K(;;~rAVI.
VJ". f.J
~=~
..1-~30 ~
j
'Z1lA.'V,
-J '
ffjk i
'(If\.;;
\
M4"'.\-
KC f' 1-r;;;.
~
~qJ~,~
?>f(M~
t~,o6~~kf~t
f