Net Torque - Physics - Solved Paper, Exams of Physics

Download Net Torque - Physics - Solved Paper and more Exams Physics in PDF only on Docsity! AAS w Physics 124 - Analytical Physics FIRST COMMON HOUR EXAM Monday, Feb. 21, 2011 Professor Ron Gilman => = SIGN HERE NOW: The exam will last from 9:40 - 11:00 p.m. Use a #2 pencil to make entries on the answer sheet. Enter ID information items 2-5, now, on the answer sheet before the exam starts... In the section labeled NAME (Last, First, M.I.) enter your last name, then fill in the empty circle for a blank, then enter your first name, another blank, and finally your middle initial. Under STUDENT # enter your 9-digit RUID Number. Enter 124 under COURSE; you may ignore the section number. Under CODE enter the exam code given above. During the exam, you may use pencils, a calculator, and one 8.5 x 11 inch sheet (both sides) with formulas and notes. There are 18 multiple-choice questions on the exam. For each question, mark only one answer on the answer sheet. There is no deduction of points for an incorrect answer, so even if you cannot work out the answer to a question, you should make an educated guess. At the end of the exam, hand in the answer sheet and this SIGNED cover page. Retain the exam questions attached for future reference and study. When you are asked to open the exam, make sure that your copy contains all 18 questions. Raise your hand if this is not the case, and a proctor will help you. Also raise your hand during the exam if you have a question. Please have your student ID ready to show to the proctor during the exam. Possibly useful information: at the earth’s surface g = 9.8 m/s’, G = 6.67x 107! Nin?/ke?, Mears = 6X10" kg, rearth = 6.4%108 m, Thoap = mr’, Tectidaise = (1/2)mr?, Ieotiatan = (2/5)rar?, and Istick aboutenad = (1/3)ml*. 1. Two masses hang from massless ropes attached at different radii to a 1-kg pulley, The left mass, m, = 5kg, hangs from a radius of 0.2 m; the right mass, ™,z = 10kg, hangs from a radius of 0.1 m. There is friction between the rope and the pulley. The pulley is supported at itsg cm. What is the net torque on the pulley from the forces acting on it? Ry =(m m) 4 Consider the cm, of the puley AL The torque of F, & germ @_ oN) (Stee cur of this fore =0) ©) °} GON The torques of F (Fe-mgn) d) 196N Oma Fy (%,=W,Gt) Compensate ) WEN egch ofier, Thus, [ a, 2% =0 Feng ¥ E> M24 Your professor puts several objects on an inclined plane. All roll without slipping down the inclined plane. Which gets to the bottom first? a) hollow sphere, radius r Fuerag Conservation : E= keP =Const 0) b) solid cylinder, radius r 2 2 =, Caw be closen c) solid cylinder, radius 2r Sw 4 Feo =ygh =cowst ( we Cd) _solid sphere, radius r) ny —the Speed of theam, OF & ‘ hollow cylinder, radius 2 ©) hollow cylinder, radins 2r Swe" [4+ Zea \=mgh == Otte berttow, lie Speed. of an The flywheel of an engine rotates at 10 rad/s with an applied power of 10 ect woth he. . eee . ae? . W. What is the frictional torque in the the engine? syratles +o apiél a) 01Nm be the qizatest. ce) 10Nm a) 100N-m e) Cannot be determined from information given. ad uw = 10 = » 00 —> the angle swept by P= Thitiou ‘ im 18 & fre! be tadeus yeckor im . {| power - B_ wo a7 l\Aem Veiction Trriction A e jo Ss 9. A 200-kg Physics Professor, being utterly frustrated with the students’ re- sults, turns into a spherical black hole. Find the professor’s Schwarzschild radius, p= 26M 26.61 200 a) 1-10 m 5s ce (3x08 )™ c) 1-107? m ~2S a) 3-10-? m = Slo Mm e} 1-10°%m 10. The Martian moon Deimos has a diameter of about 12.6 km and a mass of about 2x10" kg. Treating it as spherical, how fast do you have to throw a ball so that it circules Deimos, 2 m above the surface, so that you can catch it? > a) <2m/s wo G Mam My _ te gent force b) in the range 2 + 4 m/s Ra ~ “Rye piuides c) in the range 4 > 6 m/s d) ‘in the range 6 > 8 m/s etal accelembon e) >8 m/s Ay= Ma ~ A ? 5. ) / CE = \grw lle’, 210° a GS iat DSK 12, 640m 11. Two solid spheres, each with a mass of M = 10kg and radius & = 0.1m, touch one another. What is the magnitude of their gravitational force of attraction? . — oo. Mm? ary (io kay a)_ON FeGl. = 60 —= Q ORY kg? (0.2m) c) 3.4¢10°N d) 6.7c107N c2RO = [,675*10° “A e) 9.8010'N 12. Titan, a moon of Saturn, has a 16 day orbital period and an orbital radius of 1,222,000 km. What is the mass of Saturn? a) _< 1x1078 ke c) in the range (0.1 > 1) x10 ig d) in the range (0.1 4 1) x10” kg e) > 1x10” kg Titan 2 m vt. Gt Cn Cenk ek, war G Mele Ms Se Gx q 13, 14. 15. A satellite with a mass of 10kg was launched into a circular orbit 1000 km above the Earth’s surface (the Earth's radius is 6.4- 10° m, the Harth’s mass is 6- 10%kg). What is the total (kinetic + potential) energy of the satellite? Take the potential energy to be zero when the Earth and satellite are infinitely far apart. a) 13-1087 ES = (Cimular obct) = - ~~ 6 Mem Ms b) 2.7-108J c) 2.7: 1083 d) BAT) tt Gwe oanaty e) —54-10°9 tg? 2 Tax tofm A tall cylinder is partially filled with water. The cross sectional area of the cylinder is 2 m?, and on top of the water is a lid, tightly sealed against the sides but floating on the water. What is the change in pressure ai the bottom of the cylinder when several students (one shown) with total mass 200 kg stand on the lid? TE _ wokg 443 Ke AP= oa Zam = 480Re ©) a) There is no change in pressure. b) 100 Pa c) 200 Pa d) 980 Pa 1960 Pa A rectangular wooden block of weight W floats with exactly one-half of its volume below the waterline. Masses are stacked on top of the block until the top of the block is level with the waterline, This requires 20 g of mass. What is the mass of the wooden block? a \ \ = the Vodice 20 ma = Pw = l of He Bock , C208) nH = Des Mass ae (m+ 0.02kg)g = Ow QV M*0,02Kg 9 Y= o.ozk¢ mn ” 16. In a pipe of radius 0.1 m, the water flow is 2 kets past a certain point. ‘What is the speed of the water further along the pipe where it expands to a radius of 0.12 m? Covtinuity equation : ay A, Wy Aa b) 1.7 m/s ) 2.0 . Aion wm kee m j sah =, f= 03 (Bt\" = 1.39 Me e) 2.9 m/s 17. A wshaped tube has mercury in the bottom, with density 13.6 times the density of water. 10 cm of water are poured into the right side. How much higher is the top of the water on the right side than is the top of the mercury on the left side? a) 0.7 om b) 0.8 cm hi C2) 9.3 em} iy 9 d} J0cm e) 186cm Out lovel 0, the pressure must be the Same Wn Goth tulles. Tuas, Pmgha=pwgh, hy~ Puts. bay Wem omdem hh, = 18. Water in a tube flows at 2 m/s. What is the change in pressure at a point =(Dem ~0, Then, 1 m higher where the water flows at 1 m/s? Assume the density of water nw - is 1000 kg/m’. a Q3cm a} -8300 Pa } b) -6800 Pa c) 0 Pa- the pressure does not change d) 6800 Pa e) 8300 Pa 2 P+ eqh Epo = Coust Prpgh rZPo = Bepghst Low, AP=P P= 5 (uur) aq (hiebe) = = 4 keg _ me? 7 / . 5 & (DOD mm? (A ‘\~ (0008. 14.8 2 ¥ Im *~ 2300 Pa