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Unformatted text preview: NAME (Print): UNIVERSITY OF WATERLOO
DEPARTMENT OF PHYSICS
PHYSICS 125
WINTER 201 l MIDTERM EXAMINATION Date: February 15, 2011 Time: 8:3010:20 am. I.D. #: X PROFESSOR: DIVISION #1 2
SIGNATURE: IMPORTANT INSTRUCTIONS  READ CAREFULLY TO AVOID PENALTY Use PENCIL. Mark your ID# and three digit “Section number”. Check that you have not missed, or put double marks in any row in the answer ﬁeld. (Keep sheet face down
when not in use.) Fill in name, etc., at upper right on computer sheet and on this page. IIAND IN SHEET AND BOOKLET SEPARATELY. Booklets will be returned to the
students later. Check that your exam has 13 questions. First 8 are worth 10 marks each and the last 5
are worth 4 marks each. Formula sheet is attached There is no penalty marking for incorrect answers. However, in the event that the
computer sheet cannot be completely read, credit will be given to correct answers only if
work is shown in the space below the questions in this booklet. If you need more space for your calculations, use the blank pages at the end of the
booklet or use the back of the previous page and label it with the question number. Good luck! ! g = 9.8 m/s2, 1,, =10‘ZW/m1. Circle your Section: R. Jayasundera (Mechanical and Geological) R. Jayasrmdera (Management) Physics 125 Midterm Examination Winter 2011 Page 2 of 8 1. Figure gives the position of a 20 g block oscillation in SHM on the end of a spring. The
horizontal axis scale is set by t3 = 40.0 ms. What is the maximum kinetic energy of the blo '2 Answer in].
(b) 2.4 (c) 3.6 (d) 4.8 (e) 7.0 mm) ' . IL
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7xio'2'M ’0'99 "/5
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1 +3.5 2. A uniform Rod of mass M and length L is free to rotate about an axis through the center
of mass. Two springs are connected to the ends of the rod and a torsional spring at the
center. If the system is set in simple harmonic motion, which statement describes the
period of small angle oscillation? (The moment of inertia for a Rod (Icm)Rod = 1/ 12 MLz) ill ,
12M ‘ r3.
= _ r
a’ T 2”‘(3(k+k2)+XLz I H
i
‘ /
 (A; ‘ 9/
T_2n 3(k1+k2)L1+12)( ‘4‘
{Q o
_ (lawn/«w c. T—Zn 4M 1 1/ \
f v /’ \
4M 4 ——> a.
d. T: *
(ki+kz+X)L1 e. None of the above .. 6 .v : idiuf =7 .64.st " 1/3. F“) k "a";
O
1 2,.  gm, mu] eke = *2“ , 4 it db
717 X4 7 L/LD‘ 17 ~f k, J A”; P3251. 8  rﬂfﬂl‘ . 611.9 — 331+ h WM? 9 co =
V’“ “Tr—d //,_
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0 J ” ,BC/ew iTam/L“) Physics 125 Midterm Examination Winter 2011 Page 3 of 8 3. A disk of Radius R is suspended from a pivot somewhere between its
center and the edge as shown in diagram. For what point will the
period of this physical pendulum be a minimum. Answer in m. (a) 1.4R (b) R (d) 0.5R (e) 0.3R
M
5’“ wm‘Q/nmzw 1‘ Q (5 D‘WJ.‘ 4. Figure shows a simple harmonic wave at time t= O and later at t = 2.6 5. Write a
mathematical description of this wave. (x,t) = 1.5 sin (0.785x — 0.604t + #2)
c y(x,t) = 1.5 sin (0.785x — 0.604t + 3 1:12)
(d) y(x,t) = 0.75 cos (0.785) + 0.6041)
(6) y(x,t) = 1.5 sin (0.785x + 0.604t + n/2) y(x,t) = 0.75 sin (0.785x — 0.604 t — n12).
( Sag Mynmf
#3 fin/«65:77; Physics 125 Midterm Examination Winter 2011 Page 4 of 8 9/; ’ﬁ/(ﬁgaC (a)
5. Two spe ers one with Power 50. mw and the other with Power 61 mw are set to be
at different distances from the detector “p”. They oscillate in phase. Each speaker by
itself will produce a sound level of 70 dB’s at “p”. What will the sound level be at “p” when both speakers are turned on. Assume speed of sound to be 360 m/s and the
frequency produced is 90 Hz. (a)76 (b) 66 (c) 64 (d) 34 zero
: 12 _. ? : .‘Z—
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( k .. ’L 6’”, .5 0 = o
4“ 5w. . was.” / B “6 p («r/(f $4. I 6. Romeo jumps into his fancy automobile and drives straight away from Juliet with a
constant acceleration of 25 m/sz. The fancy car has a horn that produces a frequency of
440 Hz. While Romeo is tooting his horn continuously Juliet experiences a change in frequency. Calculate the distance Romeo is when Juliet hears a frequency of 220 Hz.
Answer in km. (a)1.6 (b) 2.3 (c) 3.7 (d) 4.5 5,2 €07,th ’1’") a; $ﬂl..wu( take/"A:
2 3P0
f;1[(%73’) ‘7 W '5 W” W)
390%“... Z 630 :7 14. : 3'70 «11/; 1 2  we)
1!!  = (123)(«
09m; 12.54/41: Qafk'wﬂ > 3’9"“ 9» 7 Jaw, (‘anf 5'47 =. Wm hag/w samec /., hm! 72a nae/ma 44' Mirage}. 414.41 "MA @4590 Jot/l 2 2
at _— ’VgEr’ljﬁé — 4 (6'5) 7‘ a (z’¢(9} = ax' _ (770)(63) 4 (2:) f : 9995/». 2291—07 ~  AM.
.701; dékwéL M 1.3 r 2»? r 3’ Physics 125 Midterm Examination Winter 2011 Page 5 of 8 A supersonic craft moving at Mach 2 produces a Mach cone as shown. Find the radius of
the acoustic spherical wave front that corresponds to point “p” on the cone. Assume the distance sp = 17.3 m. Answer in m.
(a) 6.0 (b) 9.1 (c) 8.7 w (e) 12.4 C¢£Q=é :36:30°
I #534430 =.f. 71/9: /73/°M3°‘ : 7383 :10
O. . “Wafﬂ W 8. When a tuning fork of frequency 500 Hz is heid above the tube as
shown, resonances are found when the water level is at '
distances L = 16.0, 50.5, 85.0 and 119.5 cm from the top of
g 7 the tube. What is the speed of sound in the air? Answer in m/s (a) 335 . (c) 355 (d) 365
(e) none of these ® t'. 50.5"/67 s' "Wz‘ 3"" 5M
50' 29:6900“ go
I 1 g : (5002(4) 69
M f , 245 M15 7'" Ho Physics 125 Midterm Examination Winter 2011 Page 6 of 8 9, The amplitude and phase constant of an oscillator are determined by:
(a) The frequency
(b) The angular frequency
(c) The initial displacement alone
The initial velocity alone (d
g z Both the initial displacement and velocity 10. The amplitude of any oscillator can be doubled by:
(a) Doubling only the initial displacement
(b) Doubling only the initial speed
(c) Doubling the initial displacement and halving the initial speed
((1 Doubling the initial speed and halving the initial displacement
@Doubling both the initial displacement and the initial speed 1 l. The transverse wave shown is traveling from leﬁ to right in a medium. The direction of
the instantaneous velocity of the medium at point P is: (c) —>
(d) /‘ (e) No direction since v = 0 12. Any point on a string carrying a sinusoidal wave is moving with its maximum speed
when:
’7? (a) The magnitude of its acceleration is a maximum
(b The magnitude of its displacement is a maximum
The magnitude of its displacement is a minimum
The magnitude of its displacement is half the amplitude
(e) The magnitude of its displacement is onefourth the amplitude 13. If both the mass of a simple pendulum and its length are doubled, the period will
(a) Be unchanged (b) Increase by a factor of 2 0 Increase by a factor of 4
® Increase by a factor of 1.4
(e) Increase by a factor of 0.71 ...
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 MOHAMED
 Physics, Simple Harmonic Motion, Velocity, Midterm Examination Winter

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