jonnalagadda saj2436 Work CoE ayida 4355 3 This print out should have 40 questions Multiple choice questions may continue on the next column or page find all choices before answering 001 10 0 points The Joule and the kilowatt hour are both units of energy 19 2 kW h is equivalent to how many Joules Correct answer 455 786 W Explanation Let F 709 N d 9 m and t 14 s The power expended is Correct answer 6 912 107 J Explanation 1 W 1 J s Fd W t t 709 N 9 m 14 s 455 786 W P 1000 W 3600 s kW 1h 7 6 912 10 W s 19 2 kW h 19 2 kW h 6 912 107 J 002 10 0 points A cheerleader lifts his 59 9 kg partner straight up off the ground a distance of 0 557 m before releasing her The acceleration of gravity is 9 8 m s2 If he does this 27 times how much work has he done Correct answer 8828 19 J Explanation The work done in lifting the cheerleader once is 1 004 10 0 points You leave your 75 W portable color TV on for 7 hours each day and you do not pay attention to the cost of electricity If the dorm or your parents charged you for your electricity use and the cost was 0 1 kW h what would be your monthly 30 day bill Correct answer 1 575 dollars Explanation Let P 75 W and t 7 h day W1 m g h 59 9 kg 9 8 m s2 0 557 m 326 97 J The energy consumed in each day is The work required to lift her n 27 times is 75 W 7 h day W n W1 27 326 97 J 8828 19 J 0 525 kW h day W Pt kW 1000 W In 30 days you would use 003 10 0 points A student weighing 709 N climbs at constant speed to the top of an 9 m vertical rope in 14 s What is the average power expended by the student to overcome gravity 30 day 0 525 kW h day 15 75 kW h which would cost you 15 75 kW h 0 1 kW h 1 575 jonnalagadda saj2436 Work CoE ayida 4355 3 005 10 0 points A 105 kg physics professor has fallen into the Grand Canyon Luckily he managed to grab a branch and is now hanging 87 m below the rim A student majoring in linguistics and physics decides to perform a rescue experiment using a nearby horse After lowering a rope to her fallen hero and attaching the other end to the horse the student measures how long it takes for the horse to pull the fallen physicist to the rim of the Grand Canyon The acceleration of gravity is 9 8 m s2 If the horse s output power is truly 1 horsepower 746 W and no energy is lost to friction how long should the process take Correct answer 120 004 s Explanation The work against gravity which is necessary to raise the professor to the rim of the canyon is given by W m g h 105 kg 9 8 m s2 87 m 89523 J If the horse s power output is one horsepower then the the time for the horse to provide the necessary work is given by tup W Poutput 89523 J 746 W 120 004 s 006 10 0 points Potential energy and kinetic energy are forms of what kind of energy 1 chemical 2 5 heat Explanation 007 10 0 points A Joule is a measure of 1 density 2 distance 3 volume 4 momentum 5 energy correct Explanation 008 10 0 points Shawn and his bike have a total mass of 58 7 kg Shawn rides his bike 0 77 km in 13 9 min at a constant velocity The acceleration of gravity is 9 8 m s2 What is Shawn s kinetic energy Correct answer 25 0184 J Explanation Shawn s velocity is v d t Thus his kinetic energy is 1 K mv 2 2 0 77 km 1000 m 1 min 2 1 58 7 kg 2 13 9 min 1 km 60 s 25 0184 J 3 mechanical correct 009 10 0 points Tim with mass 71 6 kg climbs a gymnasium rope a distance of 2 m The acceleration of gravity is 9 8 m s2 How much potential energy does Tim gain 4 electromagnetic Correct answer 1403 36 J 2 nuclear jonnalagadda saj2436 Work CoE ayida 4355 3 Explanation Let m 71 6 kg h 2 m and g 9 8 m s2 Potential energy is U mgh 71 6 kg 9 8 m s2 2 m 1403 36 J 010 part 1 of 3 10 0 points A 40 0 kg child is in a swing that is attached to ropes 2 30 m long The acceleration of gravity is 9 81 m s2 Find the gravitational potential energy associated with the child relative to the child s lowest position under the following conditions a when the ropes are horizontal Explanation Given 36 0 Solution The child is a distance cos from the attachment point so h2 cos and Ug mgh2 mg 1 cos 40 kg 9 81 m s2 2 3 m 1 cos 36 172 366 J 012 part 3 of 3 10 0 points c at the bottom of the circular arc Correct answer 0 J Explanation Solution The child is at the lowest point so h3 0 and Ug mgh3 40 kg 9 81 m s2 0 m 0J Correct answer 902 52 J Explanation Basic Concept 013 Ug mgh Given 2 30 m m 40 0 kg g 9 81 m s2 Solution The child is at a height h1 from the lowest point so Ug mgh1 40 kg 9 81 m s2 2 3 m 902 52 J 011 part 2 of 3 10 0 points b when the ropes make a 36 0 angle with the vertical Correct answer 172 366 J 3 10 0 points A block of mass m slides on a horizontal frictionless table with an initial speed v0 It then compresses a spring of force constant k and is brought to rest v k m m 0 How much is the spring compressed x from its natural length mk g r m correct 2 x v0 k v2 3 x 0 2g k 4 x v0 gm 1 x v0 jonnalagadda saj2436 Work CoE ayida 4355 3 r Anyone who checks to see if the units are correct should get this problem correct 014 10 0 points A bead slides without friction around a loopthe loop The bead is released from a height of 11 6 m from the bottom of the loop theloop which has a radius 3 m The acceleration of gravity is 9 8 m s2 From conservation of energy we have K i Ui K f Uf m v2 m g 2 R 0 mgh 2 v 2 2 g h 2 R …