Download Physics Exam 2 - February 2009 - Prof. Michael J. Nolan and more Exams Physics in PDF only on Docsity! Phys 231 Exan 2 February 20, 2009 ? t l NAMEI\I!\l\hI . Recitation (circle one): 9:30 l:00 Keep in mind that I must be able to follow your work in order to giv€ you credit. This is especially fue when awarding partial credit. A wong answo with the right methods gets partial ffedit. IfI cannot figure out the methods then no credit even ifthe answer is correct. Answers must be justified. An answer by itselfreceives no credit. Units! Vectors! l) (20 pts) The picture below shows an object sriding down an inclined plane with an extemal force Fpushing up the plane. The kinetic and static coefficients of friction are specified. ur. tt " "o--ainui" ,y.t.,aligned with the plane as shown. Also assume that the mass never leaves the plane. 1V" = 2.0 m/s M = 1.5 kg F = 5 . 0 N 0 = 3 0 " W= .25 F, = .75 a) In the space below, draw a force diagram for the mass M. b) Calculate the frictional force. Force is a vector; speciry it direction. ? , J -a -)'- C J I t { 11 = ,1 t"l ',y'^"'.\ *s - 1 , z . r - )q r i \ ) ( ' l .Y€) \ " ' (3 \ ' ) M { * - + - l . r r N + X d i u . a f i u , c) In the space below, sketch a graph ofthe X co-ordinate (vertical axis) versus time (horizontal axis). Be certain that your graph has aris labels, units, hash marks and numerical scales. X(') \ ; Xo-r u ' . ' ) 6 It ,", - Liu r.-^-* - 1 7 i t - 1 7 1 X o : \ JY t t s ) I . Y U d) In the space below, sketch a graph ofthe magnitude ofthe total force acting on M (vertical axis) versus time (horizontal a,ris). Be certain that your graph has axis labels, units, hash marks and numerical scales. 1 :1 r . r / \! t,* ^[r . ) \ . / 4 / l w1t\. J t , - ( , Z r r" t l \ ' r ' ( -- I r.r- l,.t \ t s r / q r r . - | i t - r - 3) ( l5 pts) The pictue below shows two masses liding on a frictionless urface (think air tracks) about oundergo a collision in one dimension. The positive X direction is specified. M1 = 4 .0 kg l M ' I - u ' Ur : +1.5 r r ls I I u r t s The graph below depicts the force on object 2 due to object I during the collision. Note the time scale ofthe horizontal axis is in seconds. There is, ofcourse, a foice on objeci l due to object 2, but no other netforce acts on either obiect. M, = 2.5 kg U2 : -4.5 m/s time (s) a) The momentum ofobject l changes as a result ofthe colrision. calcurate the change in momentum ofobject Mr . Momentum is a vector; give its dtection. i \ C u r , - { : - ' \ P , A p - : - ? u l y - r y '- [ t t s < - 1 r , " { i l t \ t b) calculate the velocity ofobj€ct 2 after the colrision. verocity is a vector; grve its direction. i n P - - \ i . . r . \ ' - k , ( , r ! . . "A$ r- l z J - An -: + i r. i l"rr"- lr ---9- " , \ ' " " t - , , \ } t ' n ' n ' - \ J r " . t ) I 'L = iV, t', * f\ 1r r ) il '= \2,.r |gX -.t.r- T) r t.! ,,1: _ - -) zr lr i ) L f j s t '. , J - l . l ' t p. : in / , l t J1 ) 2 ,.1 1.",1 c) What is the center ofmass velocity for the system after the collision? 1 7 ( l n " k , * ) l / ( ' f + o ' ) V-. = Vc ,, ! q/r : 1al , -L71 + lY2 L)2, i \ , + W t - f . r , r { r X i s 3 ) , ( 2 . - r r ) ( - v s T / G s4"-' C ) t = - l , s \ x r ) r r r I
