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Unformatted text preview: PHSX 114 Exam #3, code number 1 2 l. (10 points) The following ﬁgure shows the motion of two balls before and after a collision.
Before collision, the speed of Ball 1 is 4111/ s and the speed of Ball 2 is 3111/3. After the
collision Ball 1 rebounds at 3m/s and Ball 2 speeds away at 4 m/s. If the masses of the two
balls are both 1 kg, which one of the following statements is correct? Before C(JuiSion Alter Collision © @
<— —> Momentum was not conserved during the collision so there must have been some
external force acting that we're not told about.
b) Kinetic energy was not conserved during the collision 4?! =2 l [<5 (3124 —. 1.523276%
c) The momentum change for Ball 1 is +7kg m/s
d) The momentum change for Ball 2 is +7kg m/s ‘lﬁil k3 (313 z: 1 l<j / 6) All of the above statements are true. ’)
41+sz i: 0 P55 noi 2. (10 points) A 2000 kg open cart rolls along a frictionless track at a speed v0. The rain begins
and ﬁlls the cart at a rate of 0.15 kg/s. If the speed of the cart is 7. 4 m/s at 20 minutes after the rain begins, what is the cart’s original speed 120? m ram :2 0 [& KS/g x 20 X 6155:— l goka— ;; 3333/: “books as :Coookgrlﬁokj J 7:“1 c 8.5m/s m ”U 2 ZoooﬂgD W .__ M
e 9.311113 0 1,000 X7Vqﬁ/5h‘ 8‘ /§_ 3. (10 points) Amy (65 kg) and Gwen (22 kg) are
standing on slippery ice and push off each other.
If Amy slides at 6 m/s, what is the magnitude of
the Gwen’s linear momentum? horeuﬁl"
6 E O 8 O s P526 1‘41:
c) 640 kgm/s after] 9W3,“ ‘
d) 525 kgm/s ‘
e) 750kgm/s [3/ +9? 13A”?
Q z). ‘92:; l = Wei.
Giff: 631(6): 6—621—SCEOK8F“ PHSX 114 Exam #3, code number 1 3 4. (10 points) A tennis ball of mass 0.06 kg and speed v=38.0 m/s strikes 9
a wall at angle 0:50 degree and rebounds with the same angle. What is
the impulse of given to the ball by the wall?
1 I a) 5.3Ns VX/ =1 Vy 4?; = O b) 6.0 N s 0 :1 _, c 2.2 N s l V f l)7 3‘” ® '> ﬁzz cm
A. \ __ X 0.5
e) 7.6Ns P/ [7' I7 3
:2 _ s . e N ~ 8 . 5. (10 points) A 5.0 g bullet is shot horizontally into a 4.0 kg block of wood that is at rest on a
wooden table. The block and embedded bullet slide 0.04 in across the table and come to rest. What was the initial speed of the bullet before impact? Take pk = 0.20.
a) 506 m/s smolﬂﬁ “Hal Cm” “Wk : . /
O‘OOSKS a U0 ‘2: L41 o.ooS)l<Sx U0 0) 630m/s d) 77.0m/s bullet 'l‘ lolock ghC/LK on "l’kLle. _. ) 1420m/ 2. e S ~g(4.oo§g3) U; 2 é}.oasz<3)3 :70le . l . S“ 2
Elm 00) =t8‘” xo.2><4.om =>Uo=3Ilg—L ‘Hoo‘; ‘5}
6. (10 points) Find the angular acceleration of a pebble stuck to a bicycle tire of radius 0.5
m as the bicycle accelerates from rest to 10mph (4.47m/s) in 3 seconds. Assume the
ac   ._ 'n is constant in time. a) 3.0 rad/s2 4‘47M/s — O M
b) 6.7rad/s qt 2 1 l~ CH /32
c) 0.75 rad/252 Cl 5 $
M
2313:2322 0< = * : r“ 4’“ 2 some a
Y' oxsm 3 ' 7. (10 points) Calculate the torque about the front support of a diving board, exerted by a 62 kg person 3.0 m from that support?
a) 4.8 N m 6 2 K3 b) 22.7N : l< , :41 xi .
c) 685an L C 6a 5X ﬁ‘ 832 m
e)l2*82mm \L 3W“ 2 [$23 ALM ”“8 PHSX 114 Exam #3, code number 1 4 8. (10 points) An oxygen molecule Whose total mass is 5. 26x1926 kg consists of two oxygen
atoms. The distance between the two oxygen atoms is 1. 2x10’10 m. If the oxygen molecule is
rotating at 1.5x1012 rad/s about an axis perpendicular to the line joining the two atoms and
midway between them, what is the angular momentum of the oxygen A
molecule? .
.‘2K 4:0 1 i
1: 526x10 K5016 MD M I
g 1': l~‘imc_q'é’\<5m ' E
d) 53x1029kgm2/s 5
e) 29x1025kgm2/s L: I 0 g z _ 121M 5 a 9. (10 points) A centrifuge rotor has a moment of inertia of 4.25 x10'2 kg m2. How much work is
required to bring it from rest to 1047 rad/s? l I 1 co__o .
)13.3kJ == =——1 .— a
:)12.3kJ W :KE 2 (W 00.)) 6021047 mol/
0 . _. m1
igig '“E 42saykSW1x<f47EQZ
wasexm 3_ 10. (10 points) When the skater shown in the ﬁgure brings her arms in closer to her body, her
angular velocity increases by 35%. If her moment of inertia with her arms outstretched is 9.2 kg m2, her moment of inertia after she bring her arms in is:
2 T‘rea"? W Skccii V“
a) 8.4 kg m . b 97ka. (as 0m {swim fjsiewx‘. c) 6.8 kgm.
m Lo d) 5.
e) 7.2 kg m2 Iw%21®' ._. (do
L=L0 ”'1.
: l‘z‘ﬁ ‘m X 1.35 ' :6~%\3m1 PHSX 114 Exam #3, code number 1 Extra credit problem (10 points): 11. (10 points) A playground merrygo—round has a moment of inertia of 600 kg m2. When the
merrygo—round is at rest, a 20 kg child runs at 5.0 sz along a line tangential to the rim and
jumps on, landing on the rim a distance of 3.0 m from the rotation axis of the merry—go—round
(this could be Viewed as a complete inelastic collision). The angular velocity of the merrygo— TremT Wmerry—ja—FOWWQ “moi Chick 0‘ :L round is then: a) 0.56 rad/s
b) 0.45 rad/s c I 1 rad/s
d) 0.38 rad/s
e) 1.2 raJs 0\V\ {Soimm $6,$+€W\ 1 Lo
S. M
Lo 2:. 20%). {am}. a As ...
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 Spring '08
 DAVIS

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