PHYS 211 Exam 2 Spring 2019 v1 Solutions

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PHYS 211 Exam #2 Penn State Harrisburg Spring 2019 DO NOT TURN THIS PAGE UNTIL INSTRUCTED TO DO SO Name (print clearly): SO(U\'Yw\s PsUE-mail:___ Qimg 3EE@PSu . edn Section (200 or 400): By signing below, | acknowledge that | am aware of Penn State Harrisburg’s academic integrity policy. | further attest that the work | am submitting with this exam is solely my own and was developed during the exam. | have used no notes, materials, or other aids except those permitted by the instructor. | also agree not to discuss this exam with anyone outside my section of the class until the exam has been returned. Signature: Instructions: This exam is closed book and closed notes. You may use the equation sheet distributed by the instructor with the exam. In addition to the exam and equation sheet, you may have a calculator, pencils or pens, and an eraser on your desk. All other materials must be put away in your backpack and completely out of sight to you and those around you. You have 75 minutes (1 hour and 15 minutes) to complete the exam. The exam will be collected promptly at the end of the allowed time and no extra time will be given. Please keep your papers covered at all times and avoid looking around the room. The exam consists of 8 multiple choice problems and 3 written problems. All answers and work must be written on the test sheets to receive credit. If you need additional space, please ask the instructor for a blank sheet of paper and staple it to the back of the exam booklet before turning it in. Multiple choice questions are indicated by bubbles. The answer bubble must be clearly filled in on the exam sheet (see example below). If | cannot tell which answer you intended to be your final answer (because you filled in more than one bubble or didn’t erase fully) you will receive no credit! Correct: Incorrect: Incorrect: Really Incorrect: O One O One O One O One O Two O Two O Two O Two @ Three O©rhree © Three O Four O Four O Four O Four O Five O Five O Five O Five Multiple answer questions are indicated by square boxes. For these problems multiple answers may be selected. One Two Three Four Five OoOmEOm Written problems require that you show all work and write the answer in the box provided to receive full credit. Write answers in these boxes (3 sig figs) value units = 1.23 | m Page10f8

PHYS 211 Exam #2 Penn State Harrisburg Spring 2019 Multiple Choice (8 problems, 4 points each, 32 points total) 1. A potted plant is set on a bathroom scale in an elevator. When the elevator is at rest, the scale reads 100 N. If the elevator is traveling downward and its speed is increasing, the scale will read: O 100N @ Llessthan 100N p s calt reads 1 O More than 100 N , n O It depends on the mass of the potted plant ’|"’5 l ‘\, O It depends on the mass of the elevator V- & O It depends on the velocity of the elevator mq > (oo N ‘( O It depends on the species of the plant Mg?n, so nemy A block on an inclined ramp is connected to a wall by a spring. The spring is stretched far past its equilibrium length, and the system remains at rest. A free-body diagram of the block would include which of the following forces? A gravitational force pointing tho) theramp (net L o reny ") A ténston<orce pointing ouWfir to) theramp (e f*opk\ A normal force pointing up (paralletto) the ramp (nis Ly, ner ll 4o o) A Qb@r-:gpointing down (parallel to) the ramp (ro rocker ens e A friction force pointing up (parallel to) the ramp v~ A spring force pointing tip{parallel to) the ramp (c‘.u "y e O@000O0 ‘_-'"f’ !) FSQ“") "3 You are riding a Ferris wheel which is experiencing uniform circular motion. At which of the points shown must the normal force n exerted on you by the seat be greater than your weight mg? @ A O B C O Cc¢ Nz wmy O D mg>n & O None, the normal force is afi;@sm&er than your weight Ry o O All of them, the normal force is aw than your weight D B AN " a Page 2 of 8

PHYS 211 Exam #2 Penn State Harrisburg Spring 2019 4. A miniature model train travels at constant speed of 10 cm/s around a circular track which has a radius of 2 m. Which of the following statements about the train are true? Select all that apply. 2 B The train’s acceleration has a magnitude of 0.5 cm/s?. —_— Q, __f - Q_o_‘,"‘/il = '.f:o u';g’ The train has no tangential acceleration. (const spead) " L. aulal O The train has nmlon (st have Gt Torm ) = 0.5 g™ O The train’s veloc1ty and acceleration vectors are Wto one another. 7 O The train’s veloeity is constant. O The net force on the traini ’\ s & veer, Chames divectin) Q a,~¥°,.. ZFrT\‘Q . 5. A red cart with very little mass moving quickly to the right bounces off of a blue cart that has a very large mass and is initially at rest. Afterward the red cart moves away quickly to the left, while the blue cart moves off very slowly to the right. Which of the following statements about this scenario are true? Select all that apply. O The redcart exerted a Iafie on the blue cart than the blue cart exerted on the red cart. O The red cart exerted a sm rce on the blue cart than the blue cart exerted on the red cart. The red and blue carts exerted exactly the same amount of force on each other. N3L guoranrees s ! The red cart experienced a larger acceleration than the blue cart. O The red cart experienced a smaller acceleration than the blue cart. O The red and blue carts experienced exactly the same magnitude of acceleration. Before After — e < e g Blue = Blue o U o U o U @) OVees lorge. Thon AN e 3 ’ \ Lol witl b lerper A Q«‘ € rh g gumi. Jov. i Some Force, bor dieent masses (cad b 4. accelenaim 6. You measure the friction force between a block weighing 20 N and a perfectly level aluminum track for different magnitudes of horizontally-applied force P, producing the graph shown below. According to your data, what is the coefficient of static friction between the block and the track? O 0.050 ,Elm,‘:gm O 0.150 SN) 6—/ @ 0.250 [ I N 0" st . T 1 S = n i | | | | i O 0.60 ’E,m F e A alooi O 1.00 “. 9 3____‘_ —|_ 1 1 | 1] " 1 2 T O 167 B 1D 0, AR AR S - 76t 0oy L e n ~m4 e o, Y ) TLtr\ ’I’Sl\w"“ YN ¢ =6 7/50 Page 3 of 8

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PHYS 211 Exam #2 Penn State Harrisburg Spring 2019 7. A crate weighing m&y;?sitting at rest on a horizontal surface. The coefficients of friction between the crate and the surface are u;, = 0.3 and pg = 0.5. If a horizontal force of magnitude 60 N is suddenly applied to the crate, what will the magnitude of the frictional force on the crate be? O 20N ; 282 ,\Q Cleck * f,Mp:/u;n-:)mn. % O 50N £ 5 P F oomanco = Nemyzo - V=g =loe O 60N Z i O 100N fi\fi "g,nm;; i (O'S)(l(’bN\ = Son Il . v 0 P7 —Fg,mx, Se (ke U shQL . ": Wikl he (k/ aw d j(;:}AKV\ 1(0,3)(1060)\ - 3b¢/ 8. You take data of velocity vs. time with a Smart Cart carrying heavy masses and generate the plot shown below. If the net force applied to the cart during this motion was a constant 4 N, what was the total mass of the cart and heavy masses? V(W/S) 20 ---r--roo o O 0.667 kg ; ! : : | ; O 1.00 kg L R e i Ry o ahbd O 2.00kg i : i ; : ; -’D 1 1 1 1 I 1 O 3.00kg ZF':‘{Y\;\) / 1 =D moviom, 1~0"":"“:"' 4 "‘:"":"“: @ 6.00kg : i : l ; O 12.0kg 2 F'/‘iu, a F.—.mcjr.\ek'_ e i ol skl st i bt ; A : i : ot a AV 2.0 m(s —O Mg 0005 70 15 20 23 30 ®) " B¢ 3.0s -os = Z M z /% ¢ .z t‘z?‘ = (e %—F.‘ = - _7’,- r'//” C j Page 4 of 8

PHYS 211 Exam #2 Penn State Harrisburg Spring 2019 Medium Problem (18 points) 9. A cart with a large sail on it rolls down a ramp inclined at an angle 8 = 22.5° through air of density p = 1.22 kg/m3. The cart-and-sail system has a frontal area of 0.0450 m? and a drag coefficient of 1.15. You may ignore friction. a) Draw a free-body diagram of the cart-and-sail system. b) If the system reaches a terminal velocity of v = 6.30 m/s% what is the system’s total mass? Draw FBD here D= lzf CAVY, o-d e hat all of ruer! 2 D=2t /o) (L1SYootsor)630m) = [ 232 N -—D Terminal wlosity Mans d=o! ;. / 2 Fx =max =© mg sme—D=O mgsinefr.b M D 25N < 5 33¢0 89 ke - 35[»9’ = 7'M{L s.h'lZ.S ov, th Lm’(“‘:, A _PCA Ve 24 sinP w1 2z Write answers in these boxes (3 sig figs) value units m=| ().334 lcfi Page 5 of 8

PHYS 211 Exam #2 Penn State Harrisburg Spring 2019 Medium Problem (18 points) 10. The Wave Swinger is a carnival ride in which the passengers are seated in a swing that is connected to a central crossbar by a cable. The passengers are then spun around in a circle of radius d as shown in the diagram below, where the passenger and swing are represented as a particle which has a total mass of m = 80 kg. When the passenger has reached a constant rotational speed, the cable makes an angle of 8 = 30° from the vertical. Ignore drag. a) Draw a free-body diagram of the child and swing (i.e. the circular mass in the figure). b) What is the tension force F, exerted by the cable? c) |If the passenger is a distance of d = 5 m from the axis of rotation (i.e. from the center of the circular path), how fast is the passenger moving? Draw FBD here e Crossbar { e, 2\ ‘sl "‘ : - Cireder MmetSon: Ote rE2 Comrdinates (=] ZF-;'=MG%'-F:COSQ-M3‘—M F,o. mg . D 505 2852 N cosS coes 36° ZFr TMA F:S‘ir\e) =MG, © T Esine ~MmvV/, \/1' % Y‘E Sine mm v mM Fo kn V - Jresme (5, 905.2552MY sia3%" - § 2(g§S mis . 5AY fo5. 28 52 Sin 70 Write answers in these boxes (3 sig figs) value units F.=| 905 | N v=| 5.32 |"s Page 6 of 8

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PHYS 211 Exam #2 Penn State Harrisburg Spring 2019 Long Problem (32 points) 11. Two blocks are connected by an ideal rope that passes over an ideal pulley. Block A has a mass of my = 6.10 kg and is sliding up a surface inclined at an angle 8 = 26.0° from the horizontal. Block B has a mass of mg = 5.00 kg and is accelerating downward at 1.53 m/s? Ignore drag. a) Draw free-body diagrams for each block. b) What is the tension in the rope connecting the two blocks? / c¢) What is the coefficient of kinetic friction between Block A and the ramp? From FBDof ®: ZTF emax mgq —-T “Ma gy © Mg §-mgay =T (S.cnwj)( Qro8 - ng,..,"\ s Draw FBD of Block A here T: YI.35 N Frme FBD of A ZFx<mas EEy= 0y T_&-MASS."‘G :MAQAX n'mAficQSO =0 f ' V):-W)AScoSe@ ez T -magsine ~Ma Qpy @D Draw FBD of Block B here and shnc -f\r, T Mhen (‘i ) |, Wt tan (vWL;Ml uS;»J C(Axf C(B?‘@ ) _ | s Me = fe o 1 TMagsm0- M G l s Ms §cose L U135 - (i) (130 E sin 268 - G loks)(1.634%) Mg /‘A"' (L-W"ﬂ (4-¥0MY) 65 26.0° Write answers in these boxes (3 sig figs) = 0.]o®ISS value units r=| 4914 | N - S.3maznN 573. s8N p=| 0108 |@=d Page 7 of 8

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PHYS 211 Exam 2 Spring 2019 v1 Solutions

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