Fall 2008 Physics 105 sections 1 and 2 Exam 3 Colton 2 3669 RED Barcode Here Please write your CID 3 hour time limit One 3 5 handwritten note card permitted both sides Calculators permitted No books Constants some formulas g 9 80 m s2 G 6 67 10 11 N m2 kg2 Mass of Sun 1 991 1030 kg Mass of Earth 5 98 1024 kg Radius of Earth 6 38 106 m Radius of Earth s orbit 1 496 1011 m Quadratic formula x Ipt mass mR2 Isphere 2 5 mR2 Ihoop mR2 Idisk 1 2 mR2 Irod center 1 12 mL 2 Irod end 1 3 mL2 b b 2 4ac 2a Keep four significant digits throughout your calculations do not round up to less than four When data is given assume it has at least four significant digits For example 15 meters means 15 00 meters You are strongly encouraged to write your work on the exam pages and circle the correct answer Of course also record your final answers on the bubble sheet Write your CID above upper right corner Did you do this You won t get your exam back without writing your CID Problem 1 A 1500 kg car must travel at what speed in order to have as much momentum as a 5500 kg truck moving at 30 m s a Less than 74 m s b 74 84 c 84 94 d 94 104 e Faster than 104 m s Problem 2 In a collision between two objects with no outside forces the total momentum of the system is conserved a Always b Only when the collision is elastic Problem 3 In class a student in the rotating chair was rotating with his arms extended holding weights Then he brought his arms closer towards his body and rotated faster Why did this happen a the weights exerted a torque on his body b his moment of inertia was reduced c angular momentum was conserved d a and b e a and c f b and c g a b and c Problem 4 Did the student do work on the rotating system during this process a yes b no 1 Problem 5 Suppose Katie is floating in outer space with no forces acting on her She is at rest so her momentum is zero Suddenly she takes a ball out of her pocket and throws it The ball goes one way and she goes the other way Was the momentum of the Katie the ball system conserved a yes b no Problem 6 A large cylinder is initially spinning at 24 rad s After it rotates through an angle of 16 radians while slowing down steadily it is at rest The angular acceleration magnitude was a less than 13 rad s b 13 16 c 16 19 d 19 22 e more than 22 rad s Problem 7 Which has greater linear speed m s a horse near the outside rail of a merry go round or a horse near the inside rail a outside horse b inside horse c both the same Problem 8 Which has greater angular speed rad s a horse near the outside rail of a merry go round or a horse near the inside rail a outside horse b inside horse c both the same Problem 9 You swing a ball mass m in a vertical circle radius r with a string it is traveling at a speed v as it passes through the lowest point What is the tension there mv 2 r mv 2 b T mg 2r T mg c mv 2 d T mg 2r mv 2 e T mg r a T mg Problem 10 A ball at the end of a pendulum string speeds up as it approaches the lowest point See figure What general direction is the acceleration of the ball at the point shown a d b e c f 2 Problem11 Assuming both objects have the same mass and are drawn to scale which largest moment of inertia when rotating about the vertical axes shown a object A b object B A c same Problem 12 Compare a ball rolling down a ramp without slipping with a block ramp with no friction Which one will reach the bottom first a the ball b the block c same one will have the B sliding down a similar Problem 13 A train car of mass 6400 kg moving at 3 m s to the right attaches to another car 7100 kg that is moving at 2 m s to the left How fast do they move together after the collision positive direction to the right a Less than 0 7 m s b 0 7 to 0 5 c 0 5 to 0 3 d 0 3 to 0 1 e 0 1 to 0 1 f 0 1 to 0 3 g 0 3 to 0 5 h 0 5 to 0 7 i More than 0 7 m s Problem 14 How much kinetic energy was lost in the train collision a Less than 41600 J b 41600 41700 c 41700 41800 d 41800 41900 e 41900 42000 f 42000 42100 g More than 42100 J Problem 15 A 700 kg car enters a flat highway via an unbanked turn of radius 20 m The coefficient of static friction between the road and tires is 0 85 What is the maximum speed the car can have on this curve without slipping off the road a Less than 11 8 m s b 11 8 12 8 c 12 8 13 8 d 13 8 14 8 e 14 8 15 8 f More than 15 8 m s Problem 16 A satellite is in a circular orbit 5000 km above the earth s surface i e 11380 km from the earth s center How fast must it be moving a Less than 5 5 km s b 5 5 5 6 c 5 6 5 7 d 5 7 5 8 e 5 8 5 9 f Faster than 5 9 km s 3 Problem 17 Suppose an alien astronaut in a circular orbit around the alien homeworld 11380 km from the planet s center has an orbital speed of 7 km s How long would it take the alien to make one complete orbit a Less than 10 000 sec b 10 000 11 000 c 11 000 12 000 d 12 000 13 000 e 13 000 14 000 f More than 14 000 sec Problem 18 Titan is the largest moon of the planet Saturn scientists believe it is composed in part of rocky material Its mass is 1 345 1023 kg 0 0225 Mearth and its radius is 2 576 km 0 404 Rearth What is its surface gravity aka gravitational acceleration a Less than 1 1 m s2 b 1 1 1 2 c 1 2 1 3 d 1 3 1 4 e 1 4 1 5 f 1 5 1 6 g More than 1 6 m s2 Problem 19 How does escape velocity on Titan compare to escape velocity …