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WMU PHYS 1070 - Exam

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X2.0 107PHYS-107(13) (Kaldon-20939) Name ____________________________________________________WMU - Spring 2002 Book Title ________This is for Topic 1, not your textbook!_________Exam 00 - 000,000 points Sample – Not a Real ExamRev. 5/16/00 Tu · Mod. 5/23/02 ThState Any Assumptions You Need To Make -- Show All Work -- Circle Any Final AnswersUse Your Time Wisely - Work on What You Can - Be Sure to Write Down EquationsShort Answers Should Be Short! - Feel Free to Ask Any Questions“The Force Is Strong In This One.” Darth Vader in Star Wars (50,000 points)1.) Linda is shoving a big crate of parts across the shop floor. She is applying a force,F = 100. N, at a standard angle of 320°, and yet the crate is only sliding horizontally andat a constant speed. (a) How do you explain that the motion is only in the horizontal?(b) How do you explain that v = constant, when there is clearly a force being applied by Linda onto the crate?(c) Find the x- and y-components of the applied force.(d) The normal force, FN, is the contact force between the crate and the ground. It is perpendicular to theground. Since the crate is not moving in the vertical, you can figure out the magnitude of the normal force.Hint: It is not just equal to the weight of the crate.(e) Because the crate is moving at a constant speed, you can easily find the magnitude of the friction forcebetween the floor and the crate, as well as give the standard angle of the friction force.Physics 107 / Sample Exam 00 Spring 2002 Page 2When It Absolutely Positively Has To Fall (50,000 points)2.) Jill from FedEx™ is riding the elevator to deliver some packages. (a) If the elevator was accelerating up,does Jill feel heavier or lighter? Why?(b) The loaded elevator has a mass of 500 kg. What is the weight of the elevator?(c) If the elevator is just sitting there, find the force that the cable pulls up on theelevator.(d) If the elevator is accelerating up at 2.23 m/s², find the force that the cable pullsup on the elevator.(e) The cable breaks and the elevator falls. What is the net vector force on Jill (m = 58.5 kg)?Round and Round We Go, Where We Stop, Nobody Knows (50,000 points)3.) Consider a future space station that is rotating to try to provideartificial gravity. Speed is defined as distance/time. (a) Find the speed ofthe man’s feet as they go around and around, if the outside radius of thestation is 4.00 m and the station makes one complete revolution every0.625 seconds.(b) What is the centripetal acceleration, ac, of the man’s feet?(c) How does this ac compare with gravity?(d) The man’s head is 2.00 m above his toes. Find the speed of his headas it goes around and around. Hint: This will not be the same as in part (a). Why?(e) Find the centripetal acceleration of the man’s head. Is it very different from the answer in (b)?Physics 107 / Sample Exam 00 Spring 2002 Page 3A Man With A Hat (50,000 points)4.) Harold ( m = 145 kg ) wears a hat (m=0.200 kg). (a) Find the weight of the hat.(b) Use Newton’s Law of Universal Gravity to find the weight of the hat. R = 6.40 × 106 m ; the Earth has amass of 5.98 x 1024 kg, while G = 6.67 ×10-11 N·m2/kg2 .(c) Find the force of gravity that Harold himself exerts on his hat. Assume that r = 1.00 meters.(d) Find the force of gravity that the Moon overhead exerts on his hat. The distance between the Moon and theEarth is R = 3.82 x 108 m, the Moon has a mass of 7.36 x 1022 kg.(e) Which is bigger, the answer to (b), (c) or (d)? Which is bigger, the answer to (c) or (d)? Between theanswers to (c) and (d), what is the net force acting on the hat?“Here on the Frozen Tundra of Lambeau Field…” (50,000 points)5.) One football player, a running back (m1 = 90.0 kg), is running to the right at 8.00 m/s. A tackle (m2 = 123kg), is running to the left at 4.50 m/s. (a) What are their respective momentum vectors, rp1 and rp2?(b) What is the net momentum before they collide?(c) After they collide, with the tackle holding onto the running back, with what speed are they moving?(d) Show that Kinetic Energy is not conserved in this collision. Hint: Find the K.E. before and after thecollision.(e) The football squirts out of the running back’s hands 1.20 m above the ground, moving at an unknownupward angle and a speed of 10.7 m/s. With what speed will the football hit the ground? Use conservation ofenergy.Physics 107 / Sample Exam 00 Spring 2002 Page 4The Deer in the Headlights (50,000 points)6.) On a beautiful moonlit night, Beatrice is zipping along the highway at 28.0 m/s. Suddenly, 100. m ahead, adumb deer jumps into the road (“Hey,” says Rodney, “I resemble that remark!”). The coefficients of friction forrubber tires on concrete are 0.8 and 1.0. The mass of the car is 1000. kg; the mass of the deer is 200. kg.(a) Beatrice is so surprised that it is a full two seconds (2.00 sec) before she can stomp on the brake pedal. Thisis called the reaction time. How far is she from the deer before she can hit the brakes?(b) If the wheels were to lock up, and the car were to skid, find the speed of the car just before it hits the deer.(c) Fortunately for Beatrice, her sports convertible is equipped with ABS (Anti-Lock Braking System), whichprevents her wheels from locking up and gives her the maximum braking force. Can she stop before she hits thedeer? Find either the distance she misses the deer, or the speed with which she’ll hit the deer. Remember thereis still the 2.00 seconds reaction time!d) Unfortunately for Beatrice, deer often travel in groups, and a second deer jumps right in front of her. There isno time to stop, she hits the deer (which is standing still) at 12.0 m/s. If the deer ends up riding on the hood ofher car after the collision, what is the speed of the deer and the car?(e) If the pressure in the brake line was 1,000,000 Pa, what height of water column would this pressurerepresent? rwater = 1000 kg/m³.Physics 107 / Sample Exam 00 Spring 2002 Page 5Bird Droppings (50,000 points)7.) One of the best-sellers of 1970 was the book Jonathan Livingston Seagull by former U.S. Navy jet pilotRichard Bach. In it, a seagull learns to fly so high and dive so fast that the silly bird went supersonic and founda sort of Zen-like experience through it all. Forgetting all that mushy stuff, and ignoring air resistance as weusually do – (a) Use conservation of energy to figure out how high Jonathan Livingston Seagull ( m = 4.84


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