Announcements Exam Formulas also on website 1 Exam 2 starts Friday a Available in Testing Center from Friday Oct 19 opening time up to Monday Oct 22 at 4 00 pm i Late fee if you start your exam after 4 pm b Covers Ch 4 5 homeworks 6 10 c Sample Exam 2 is posted on the web site and Sample Exam 2 Solutions also i As before don t look at the solutions until you ve worked the sample exam It s easy to fool yourself d There s a 3 hour time limit i Might be a bit harder than the last exam plan for a little more time than the last one e Remember to write out solutions on your exam even though it s graded via bubble sheet f We ll have same answering system i 1 pick a multiple choice answer ii 1S get a numerical answer bubble in the Second digit To be given on exam Continued from exam 1 g 9 80 m s2 Colton Exam 2 Review 10 18 07 pg 1 To be memorized Continued from exam 1 x a v t v vo at vave v b b 2 4ac 2a For constant a 1 2 at 2 v 2 vo 2 2a x xo x xo vot New for exam 2 gravity w mg PEg mgy friction f N or f N for static friction springs F kx PEs kx2 P F v Colton Exam 2 Review 10 18 07 pg 2 Exam 2 Review of important concepts Definition vave v t Definition aave For constant a If ax 2 bx c 0 x vi v f 1 Newton s Laws a 1st Law inertia r r b 2nd Law F ma i True for each object as well as for groups ii True for both x and y components c 3rd Law force pairs equal opposite 2 New for exam 2 r r Newton s 2 Law F ma r r Newton s 3rd Law F12 F21 Definition W F x Fcos x Definition KE m v2 Colton conservation of energy Ebefore Wnet Eafter Hess conservation of energy KEi PEi Win KEf PEf Wout Definition P E t nd 2 Forces a unit Newtons b free body diagrams c weight mg i don t need to know Universal Gravitation yet d Normal force e friction f N or f N for static friction f tension g pulleys h spring F kx 3 Work a W F x Fcos x i unit Joules Colton Exam 2 Review 10 18 07 pg 3 Colton Exam 2 Review 10 18 07 pg 4 4 Energy a unit Joules b Kinetic KE m v2 c Gravity PEg mgy i don t need to know Universal Gravitation yet d Springs PEs kx2 e Conserved Ebefore Wnet Eafter i before and after pictures ii include both PE and KE in E terms iii include all nonconservative forces in W 1 work occurs during the change 2 positive and negative work HW 6 Problem 4 A 166 N bird feeder is supported by three cables as shown in the figure Find the tension in a cable A b cable B and c cable C 5 Power a Definition P E t i unit Watts b Power from velocity P F v Answers 143 76 N 83 00 N 166 N Colton Exam 2 Review 10 18 07 pg 5 Colton Exam 2 Review 10 18 07 pg 6 HW 7 Problem 4 HW 8 Problem 4 Two objects are connected by a light string that passes over a frictionless pulley as in the figure One object lies on a smooth incline In the figure m1 9 39 kg m2 4 56 kg and 44 6 Find a the magnitude of the acceleration of the objects and b the tension in the string A box of books weighing 287 N is shoved across the floor of an apartment by a force of 424 N exerted downward at an angle of 34 7 below the horizontal If the coefficient of kinetic friction between the box and floor is 0 571 how long does it take to move the box 4 00 m starting from rest Answers 4 347 m s2 51 204 N Answer 2 235 s Colton Exam 2 Review 10 18 07 pg 7 Colton Exam 2 Review 10 18 07 pg 8 HW 9 Problem 3 The launching mechanism of a toy gun consists of a spring of unknown spring constant as shown in Figure a If the spring is compressed a distance of 0 127 m and the gun fired vertically as shown the gun can launch a 20 3 g projectile from rest to a maximum height of 17 7 m above the starting point of the projectile shown in Fig a Neglecting all resistive forces determine a the spring constant and b the speed of the projectile as it moves through the equilibrium position of the spring where x 0 as shown in Figure b Answers 436 634 N m 18 626 m s HW 10 Problem 1 A 20 3 kg child on a 2 26 m long swing is released from rest when the swing supports make an angle of 33 1 with the vertical a Neglecting friction find the child s speed at the lowest position b If the speed of the child at the lowest position is 1 51 m s what is the mechanical energy lost due to friction Answers 2 681 m s 49 828 J Colton Exam 2 Review 10 18 07 pg 9 Detailed Sample Exam Problem A block of mass M 25 kg slides a distance d 3 m down a ramp 30o while being pulled with a force S 75 N horizontally and the kinetic coefficient of friction is 0 2 It is also attached to another mass m 5 kg by a pulley M S Colton Exam 2 Review 10 18 07 pg 10 3 Find the normal force of the incline on M answer 174 676 N 4 Find the frictional force on M answer 34 935 N 5 Find the acceleration of the system answer 3 451 m s2 6 Find how long it takes for the block to slide a distance d 3 m down the slope answer 1 319 s 7 Find the tension in the rope answer 31 75 N d m 1 Draw all the forces on m and M 2 Write down Newton 2 for each object both x and ycoordinates where appropriate and for the system Colton Exam 2 Review 10 18 07 pg 11 Colton Exam 2 Review 10 18 07 pg 12 A block of mass M 25 kg slides a distance d 3 m down a ramp It is also attached to another mass m 5 kg by a pulley At the bottom the string is cut The block travels a distance L 1 m to a stiff spring of constant k 40000 N m and then compresses it coming to a stop The kinetic coefficient of friction is everywhere 0 2 3 Write a conservation of energy …