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Student number: SOAdrr—OUS FACULTY OF PURE AND APPLIED SCIENCE YORK UNIVERSITY
DEPARTMENT OF PHYSICS AND ASTRONOMY PHYS 1420 06 — Physics with Applications to Life Sciences
FIW 1011 Midterm examination Instructions: 1. Print your name and student number on this page in the upper left corner.
2. Check that your exam contains 7 questions.
3. The total number of marks is 80. 4. Calculators are allowed as aid.
5. Answer all questions in the space provided on this test paper. 6. Formulae are provided on the last page of this paper. 1. (22 marks, 2 marks for each question). Answer the following eleven multiple choice questions. Circle the correct answer in the answer
table provided below. a. A graph of position versus time for a certain particle moving along thexaxis is shown below.
The average velocity in the time interVal from t = 2 s to t = 6 s is 1. 2 m/s I
(22.5 m/s _  {gm 1 3. 3 ms 3 IEL‘IIIII   ,1 IHIVIIII 4 4 “1/3 2 lllii=lll 5. zero 2. flllllﬂll b. A rock hits a window, breaking the glass, and ends up on the ﬂoor inside the room. Which of
the following statement is true? I. The force of the rock on the glass was bigger than the force of the glass on the rock. @The force of the rock on the glass had the same magnitude as the force of the glass on the rock.
. The force of the rock on the glass was less than the force of the glass on the rock. 4. The rock did not slow down as it broke the glass.
5. None of the statements is true. c. How long does it take on average for a molecule of glucose to move 30 pm in cytoplasm via a
difﬁision preocss? Glucose has a diffusion coefficient of 1.1x10‘l1 111% in cytoplasm.  ' 1.0.45x105s ﬁg: not
2. 0.45x10'5s 2 { ._ is 2
3.1.4x10‘5s Jam, ,,.. d. Alex and John are loading identical cabinets onto a truck. Alex lifts his cabinet straight up
from the ground to the bed of the truck, whereas John slides his cabinet up a rough ramp to the
track. Which statement is correct? 1. Alex‘ and John do the same amount of Work.
2. Alex does more work than John
@John does more work than Alex. 4. None of the statements IS necessarily true because the angle of the ramp is unknown.
5. None of the statements is true because the force of friction is unknown e. If two particles have equal momenta, are their kinetic energies equal? 1. Yes, always. 2. 2. No, never. =_ 2%”
@No, except when their masses are equal. 4. No, eXcept when their speeds are equal 5. Yes, as long as they move along parallel lines. f. Metabolizing 1 gram—of fat can release 9.00 kcal (1 Real = 4186 J). An average man (mass
70.0 kg) running slowly requires 65.0 kcal/lcm. How many kilometers he has to run to “burn”
20.0 g of fat? Assume 20% efﬁciency of human muscles (20% of energy goes into running and
the rest into maintaining other functions in the body). @554km kcdﬁazl '
21311511  .  was? as». 3 2.77m 65 555‘s:
4 0.3611011
5 2.2km g. A ball of mass m that is tied to the end ofa cord is revolved in a horizontal plane. lfthe weight
of the ball is mg and the tension in the string is T, then the Centripetal force acting on the ball is @Tsinﬂ
2 T 3. T0050
4. mg a Tcose
5. mg  TsinG h. Consider an object on a rotating disk a distance r from the center, held in plane on the disk by ,
static ﬁiction. Which of the following statements is NOT true concerning the object? 1. If the angular speed is constant, the object must have constant tangential speed.
(2 If the angular speed is constant, the object is not accelerated.
3. The object has a tangential acceleration only if the disk has an angular acceleration.
4. If the disk has an angular acceleration, the object has both a centripetal and tangential
acceleration.
5. The object always has a centripetal acceleration except when the angular speed is zero. i. A hydrelic jack has one piston of diameter Z'cm and the other piston of diameter 8 cm. When a
100 N force is applied to the smaller piston it is displaced 100 cm. The displacement of the larger pistonis: Al Ax. 1*. z
@5250111 A K / 2
2.25 cm  _. _,_.l x, a: {on 2,6. 5'
3.50m “3"?” A: (A J Maw a“
4 100cm
5.4000m j. Figure below shows stress (0') versus strain (a) curve for bone. Young’s moduli for tensile (Y0
and compressive (Y c) stressare l
l
1. Yt = 5.8x1o9 N/rnz, Yc =1.0x10”N/m2 ill
2. Yt = 1.0x109 N/mz, Y, = 5.8x109 Mm2  i
3. Yt=1.0x108 N/mz, Yc =1.7x109 N/m2 l
4. Yt = 7.0x109 N/mz, Y0 = 1.0x105 N/m2 
@Y. = 1.7m)” N/mz, Yc = 1.0x1 0‘0 Wm2 k. The mass of a hypothetical planet is 1/1000 that of Earth and its radius is 1A that of Earth. Ifa
person weighs 600 N on earth, what would he weigh on this planet? 1. 2.4 N I [6 ﬁd‘Mn: Km
4. 96 N
. 5. 600 N 2. (10 marks). A mass, m = 0.50 kg, is attached to one end of a spring and the system is set into simple
harmonic motion. The position X of the object as a function of time is given by the following
equation; x = O.4cos(1.3t), where t is in seconds and x is in meters. The mass of the spring is
negligible and it moves on a horizontal ﬁictionless surface. c. What is the velocity and acceleration of the mass at t = 2.0 s? U": ﬂ 1:. /0.9)(I!.3) 51n[(/.3)(2_a}]: __ 0.2? (“If 0.» 7" 52‘? = W‘Wm‘ MRIs) (2613 = WW" “VJ? b. At what instant of time is velocity equal to 0.3 m/s?
.. 0,3 ;— .. (act/(£3) Jrhﬂﬁé) 0.575? : {flap3 6}
426: xz'z."{0J'769J f=£24¥s c. What is the magnitude of force exerted by the spring on the mass at t = 2.0 s? F: was (airy/0.x“? “yd :— 0.29 4/ c. How much work does the spring do to move the mass from X] = 0.1m to x; = 0.3 m? w  «59 => Kc: 4.2741 3 (Xe/“(0.5) : £9.4’4J' ’91:, N: ~[j(w raw/£7,314qu ~j(o.é>‘15'$j(oalm/7
N"; ~0.03LI(7§ 3. (10 marks) Chinook salmon are able to move upstream faster by jumping out of water periodically; this
behaviour is called porpoising. Suppose a salon swimming in still water jumps out of water with
speed 6.26 m/s at an angle of 45°, travels (projectile motion) through the air a horizontal distance
L before returning to the water, and then swims a distance L underwater at a speed 3.58 m/s before beginning another porpoising maneuver. a. Determine the distance L and the time the ﬁsh is in the air in a single jump. [email protected] ‘1/5) Cox 4310'); q_ ((3 "16.
. . — “I
Urn .. (6.25 %}(:.a (my) a 4.975 I
To FitJr: rue“? U5 :qu fafe Ar THC“ HA1: flé'lGQ(T 03:0 0 £69.92 “93) vﬁJ’ wﬁ’jé
1“: JLrS'ZS é = 2b: 0.61%)“ All? L = u“ {M : ($.43 “ﬁ/{U.‘?Ot/I): ‘W ‘“ b. Determine the ﬂange speed of the ﬁsh. ZZ—
VL r “We
{54:34, hi”
.ﬁ —% = =:'~ [/25
hae 31"? “Zr (J. 9'0 Q.
s
t
K:
L3
(1'
xi wig—“h : 6 {a
95 + /./2: 37 /‘r 4. (10 marks). In ﬁgure blow, the light string attached to the bucket is wrapped around the spool and does not
slip as it unwinds, The spool can be treated a s a solid cylinder (mass M = 5.00 kg, radius R = 0.600 m), whose moment ofinertia is I = (1/2) MR = 0.900 kg m2. a. Determine the acceleration of the bucket (mass m = 3 .00 kg) and the tension in the string. b. What is the angular speed and angular momentum of the spool when the bucket has fallen 4.0
:11, starting from rest. 7 a.) 1—
l' ‘La,
“"3
hagTam“ 772254 ,4=oiﬂ
i FQ=3HR’(§j .
771‘1'44» 144? ~ $193; :Ma q 2 m [avoid/gear “712/ £414 H _ Sparsr +j{£oaf1] a: 533'”sz T: fit/4 raj/sraotﬂ/str‘zzj: x3447. (9600 on
A223 0 +A2{g9_2)[gjg; we): MK? ’62"
w: ruff/’2 L 2;]ch 3/22 m; 4,, ray/M; we]: cm; 4’7 44% 5. (8 marks). The forces on the lower leg when the leg is extended are modeled as in ﬁgure below, Where T is .
the force of tension in the tendon, w = 30.0 N is the force of gravity acting on the lower leg and '
F = 12.5 N is the force of gravity acting on the foot. Assume that the center of gravity of the
lower leg is at its 0611th and that the tendon attaches to the lower leg at a point one—ﬁfth of the way down the leg.
Detennjm the force of tension T. J,
If“?
2!:
732mg» TOLQUES ’3qu iaaﬂvr ' DE'SICﬂﬂ'ﬂuc; rm: Lawm up new 3‘! A 71:». 27.0” ufgaewééjgm 4d. alﬂzryjz 5n, 44.921, PtUtDlUG. GVL lbw: Jutuuud. we '7~ '7": 109M 6. (10 marks). A 75.0 kg skater (John) moving at 10.0 m/s crushes into a stationary skater (Nick) of equal mass.
After the collision lasting 0.10 seconds, John moves at 4.0 m/s at an angle of 60° with respect to the original line of motion. a. What is Nick’s velocity (magnitude and direction) after thecollision?
b. Suppose the average force a skater can experience without breaking a bone is 4500 N. Is Nick? 5 bone broken during the collision? Show calculations.
6. Whose bone is more likely to break during the collision, Nick’s or John’s? Explain. &‘ {0.014(1) r @lx “if;
_ ‘9 ~— — —— — ﬁgs/9f a... mw—s
' @ * \J a _ Pk mmzépr am, I Z ’33 64.»: $394»
(#510 :(2‘: pp‘dzéo ‘X/(Dgé) air/’SOﬁJ/K/ 0%;‘95/«9379‘1‘0 1?;le 5 34a 2 2 2h ._ _ x
V W'ﬂﬁoéﬁz‘réﬂé‘vsﬁ: anew, éﬁg:  ’59::219” 7. (10 marks) A red blood cell (RBC), submerged in blood plasma, is released from rest. RBC can be treated as
a sphere (diameter d = 7.5 pm and density plum = 5.0:(103 kg/m3). The density of blood plasma is
pplasma = 9.8x102 kg/m3 and its viscosity is T] = 3.5}{103 Ns/mz. a. Draw a ﬂeebody force diagram for RBC.
b. What is the acceleration of RBC at the moment of its release? 0. What is RBC’s terminal velocity Vt when it falls through plasma? '3'; a) F; b Ar {:01 {rt.0, ¢=6i4rV=0
a. 1413 “F3: ma “‘5 [Mag/73  are/1;,” = are/gar a
014M" FP"~ y: It 5
j) '5: “gar/o (“s CL: 0. 3’0 “752’ C) (“j ‘"' 5; 'F'r—To
é‘ré‘feag  éﬁé/Emg “T759 0am
¥7¢j23.(fns¢’ Sap/.11.“) _, 549er g . I 5 2
U; t» 3 f 7530 In) /ff4gJ/5TOHUBH guano; 5% 67f{ 3.5» 103 7‘31) are», 3mg? avg, THE END ...
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 Fall '10
 StanislawJerzak
 Physics, Force, Mass, Velocity

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