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Unformatted text preview: Physics 1111 Exam #QB J I; / f a Name: 0“) ‘r' i 2 July 2009
 I w I: Order/Choice Questions (29 points) 1. A box of mass m is pushed up an incline under the inﬂuence of friction. The angle
of the incline with the horizontal is 6 and the box is pushed in the upward direction
parallel to the incline. Draw a freewbody diagram of the box with all of the applied
forces clearly labeled (use Fp for the pushing force, fk for the force of friction, etc). in" Nani lame 2. Answer T (for true) or F (for false) in the underlined spaces provided.
a) 2/ The applied force of a spring is always negative or zero.
b) T The net force on an object in free—fall (no air resistance) is always constant.
c) K Uniform circular motion requires the application of a constant force.
(1) The potential energy stored in a spring is always positive or zero.
e) F A stationary object has no forces acting on it. E) The change in an ob ject’s kinetic energy is always equal to the total work done on the object. Physics 1111 Exam #2B
2 July 2009 Name: II: MultipleChoice Questions (20 points) For each question below, choose the single best response and write the corresponding
capital letter in the box provided. There is no penalty for guessing. 1. A mad scientist stands at the top of a building of height h. Ignoring the safety of the
pedestrians below, he drops a golf ball of mass m. If the ball hits the ground at with
a speed 12f, what was the work done on the ball by air resistance? A. — mgh %m V: 7' r,
A B. mgh — %NLU% ‘
C. émv} +mgh
1 2
D. Emu; , 'I ‘ a
1,7,: A, In. of. w r
" ( {ml  E. mgh 2. An older mode car accelerated from 0 to speed 1) in a time t. arrpwer, more powerful
sports car accelerates from 0 to Be in the same time period. 'Plrariris the ratio of powers
expended by the two cars (is. in / POM)? Assume the energy coming from the engine to appear only as kinetic energy of the car. A. 1/3 : j?
}\ 13.1 a 1
V C. 3 W’ D. 9 E. 27 3. Two blocks are released from the top of a height h. Block 1 has a mass m and falls
straight down while block 2 has mass 2m and slides down a smooth ramp. If the
absence of friction and air resistance, which of the following is true about the blocks
when they reach the bottom? A. Block 2 lands ﬁrst with a slower speed. V
B. Both have the same speed but block 1 lands ﬁrst. “
C. Both have the same speed and land at the same time. D. Both land at the same time but with different speeds.
E. Block 1 lands ﬁrst with a faster speed. 4. A roller coaster is going to travel upside dowu through the top of a vertical circle circle
of radius r. In the absence of friction and air resistance, what is the minimum speed
required at the top of the circle to keep the carts on the track? A. it B' “49"”
C. 291" D. gr Physics 1111 Exam #2B 2 July 2009 0 III: Trafﬁc Light (30 points) A trafﬁc light weighing w = 135 N hangs from a. cable tied to two other = I es fastened to a
support (see ﬁgure below). The upper cables make angles of 91 r 35. egrees and 62 = 50.0
degrees with the horizontal. (3.) Find the tension in the third cable, T3. ZF: 23mm, 71—43 :0
MN —7’, J1 27—} : 7: Y a 71X 2 systems, f35'(5fn€b) ZF\:/3S‘N" 3'77y'7r2y 1’55 “ Ts ‘ 135(60535") — Ba" ((55 » J/mg 43:51
i55N " 135160535)  l3>“(£' ’70) ‘7' (wig—7
(b) Find the tensions T1 and T2. ‘ [pub N 1 T3 )3; to "if b y i 2’7 ‘ “9,2435% Harv“) = WM M
Y
Z7; "” 5560357)) 4 5’3” 5,5. " HEOTW/i/ﬁ/ A A
‘/ ' X Physics 1111 Exam #2B 2 July 2009 Name: IV: Going Through a Rough Patch (30 points) A 1.20 kg block is at rest on a. ramp of height h = 0.750 In. When the block is released, it
slides Without friction to the bottom of the ramp, and then continues across a surface that
is frictionless except for a rough patch of width 10.0 cm. The block’s speed after crossing
the rough patch is 3.72 m/s. u
H' (a) What is the speed of the Plock just before the rough patch? firW]
F 1 V'I’ if“ f I
m:th M E W1” mgr, \/
(3 ,r  7:. 1' ‘13“ A a? LIL15) :1 {[email protected]!“ {:73} (b) What is the work done by the force of friction while crossing the rough patch? a; we r w _ .2 &
Vi '3 5 %
‘14:}.72 ;
d1/06m; n/m (c) What is the coefficient of kinetic friction between the block and the rough patch? as N — 5: 2 t N
1142216sz H.771 a J]. + c] ...
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 Spring '08
 plascak
 Physics, Force, Mass, rough patch

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