PHY-2053, Fall 2011 Instructor: Dr. Bhattacharya Test ##2, Monday, October 10, 11:30 am - 12:20 pm Name Please PRINT your name PID: TO GET PULL CREDIT YOU MUST SHOW YOUR WORK Please note that you need a PINK SCANTRON for is test Questions 1 - 9 (each 6 points «8 = 48 (4 6 bonus points)) are multiple choice questions, Please read statements for each question, provide reasons, show short calculations, if necessary, and circle (both in here and in SCANTRON) the correct statement /option. Questions 10 & 11 (each 26 points 2 = 52 points) have several parts and require calculations /derivations. Please be as clear as possible explaining the notations, symbols, use of formulae, ete. Useful formulae and informations SE units: meter, kilogram, and second acceleration due to gravity 9 =9.5 m/s? due south, 2=(Sf), wom tat, zomttiat, of em) Ry + Mgt Uoyt + Syl, O Newton's 2nd law F = ma, Weight W = me Newton's law of gravitation: F centripetal acceleration ae Frictional force f, = wFiv ‘Trigonometry: are length +1, Complete the following statement: The term net farce most aceurately describes (0) the mass of an object (b) the inertia of an object. (6) the quantity that causes a displacement 2, When the net force that acts on hockey puck is 12.N, the puck accelerates at a rate of 48 m/s*. Determine the mass of the puck, DoE eat sash (@) 5.0 kg ad v cae a 485 (9 201g 3, An apple crate with « weight of 30 kg accelerates along frictionless surface as the crate is pulled with a force of 14.5 N as shown in the drawing. What is the horizontal Pee Bi |: 14.5N U319 wy (@) 1.40 mj = 20 s* Te) 129 mje S oy) (@) 0.483 m/s? 2 0.454 a (e) 2.050 m/s? 4, A 10 kg object is taken from the earth to another planet whose mass and radius are ‘owice as hig as that of the earth. The acceleration due to gravity on this planet is (a) 98 m/s* = — (b) 4.9 m/s? ve = 4h Re () 196 mje uMs (d) 245 m/s? — 4 (@) can not be determined from the given data. ce L ad hte. LORS : Rer5. An object moves due east at constant speed. A net foree directed due north then acts ‘on the object for 5.0/8. At the end of the 5.0-second period, the net force drops to zero ‘nowtons, Which one of the following statements is necessarily true? (0) The object will be moving eastward when the force drops to zero newtons. (b) ‘The change in the velosity of the abject i= disected north of west (©) The direction of the object's acceleration depends on how fast the object was initially moving. (@) The final velocity of the ob o ie directed north of cant. initially moving, i magnitude of the object's acceleration depends on how fast the object was A bull is whirled on the end of a string in @ horizontal citele of radius at constant speed v. The centripetal acceleration of the ball can be increased by a factor of 4 by ‘the following, alternative ways. 1 koeping the speed fixed and increasing the radius by a factor of 4. Ci peevine ‘the speed fixed and decreasing the radius by a factor of 4 ‘keeping the radius fixed end increasing the speed by a factor of 4, JV. keeping the radius fixed andl decreasing the speed by a factor of 4. ing the radius fixed and increasing the speed by a factor of 2 Indicate below which of the above alternative(s) la(ate) true ne (b) Land II only Tomas (d) [and V only (© Vonly fa = az v TR vy z ye Hy 7. Acar traveling at 20 m/s follows @ curve in the road so that its centripetal acceleration Ae eee! (a) 4m = (0) 8m a= Coen] Gee j- ome rot8, A book weighing 5 kg Is resting on a table. ‘The coeflicient of friction jy between the book and the table is 04. If one applies a force F to push the book as shown then the muximum eetionl foros weting athe terface between the table and the book i (a) 19.6.N and @)ISEN and TON wo (4) 49.0 N and directed tov es (©) the fictional fore is 0 IZ oN 9, A.0.25-kg ball attached to a string is rotating in a horizontal circle of radius 0.5 m., It the ball revolves twice every second, what is the tension in the string ? (@) 493 N mvt (b) 987 N tang mw v (0) 39.48. L @ on — mM ATT 7 or16, In the drawing, the mass of the block on the table is 40 kg. and that of the hanging block is 20 kg. Ignore all fictional effects, and assuming the pulley to be massless a © 8 “3 ta \* (9) Show all the forces acting on both the masses In the accompanying diagram, (b) Write down the Newton's 2nd law (not fence se*acoloration) for each mass (©) Calculate the acceleration of the entive system, (4) Calculate the tension in the string 6) Tame —®11. A boll of mass 1.5 kg is moving in a circular path of radius r = 10 m as shown in the figure with a speed of 8 m/s, (0) Please state which force keeps the ball in eiteular orbit (b) Show all the forces acting on the ball along the x direction. (©) Show all the forces acting on the ball along the y direction, (a) From part (b) and (c) find the angle 8. (©) How does your answer in part (dl) change when the 1.5 kg ball is replaced by a 3 kg ball B The hovigonbel Crmprt a pe Newel Hee Fy Sin ®t = hse OLR = Faces © hs wees a y Fys09 Fe ee = wy picey Ua by Ue uw a = tome =) & yy = 33 6 io independut mass @ Fy, Wie indepen Ve main Same,