PHYS 260 Spring 2010 General Physics Oscillations Heat and Electricity Prof K Agashe Sections 0201 0202 0203 0204 and 0205 Written Homeworks It is necessary to show the details of the derivation and not just the final answer for all problems 1 Homework 0 due before turning in Homework 1 Sign the Honor Pledge which covers all assignments I pledge on my honor that I will not give or receive any unauthorized assistance on all examinations quizzes and homework assignments in this course 2 Homework 1 due in lecture on Thursday February 4 Consider the simple harmonic motion of a block attached to a spring on a horizontal surface assume no damping to begin with At t 0 the potential energy in the spring is 25 of the maximum potential energy during this motion Moreover the kinetic energy of the block is decreasing with time at t 0 and at t 2 0 s the kinetic energy becomes zero for the 1st time after t 0 i What is the frequency of this motion ii What is the spring constant if the mass of the block is 2 kg iii If the total energy of the system is 10 2 J then what is the amplitude of the motion iv Next a drag force is added with a damping constant of 0 2 kg s At what time will the energy in the motion reduce to 25 of the energy at t 0 3 Homework 2 due in lecture on Thursday February 18 Consider the hydraulic lift in Fig 15 19 of the textbook A student stands on the piston on the left hand side whose diameter is 0 3 m and balances a 2160 kg car placed on the right hand side piston whose diamater is 1 8 m i Deterimine the mass of the student Assume that the two pistons are at the same level ii Solve problem 15 43 of textbook 2nd edition iii A second student of mass 70 kg joins the first student on the left hand side piston Determine the distance through which the the car is lifted 1 Assume density of liquid in the hyrdraulic lift is 900 kg m3 typical one for oil 4 Homework 3 due in lecture on Thursday February 25 A small homemade firework goes off 3 meters about the surface of the water where a person is diving The diver is 10 meters below the surface of the water a How much time passes from the instant the firework goes off until the diver sees it b How much time passes from the instant the firework goes off until the diver hears it When the firework goes off another individual is traveling on a boat moving at a speed of 30 km per hour away from the firework That person is standing on the upper deck of the boat also 3 m above the surface c If the person on the boat hears a sound with frequency 200 Hz what is the actual frequency of the firework s sound d If the frequency of the light emitted by the fireworks is 5 1014 Hz what is the wavelength of this light as seen by the diver For values of numerical constants refer to the textbook assume temperature of the air is 20 C 5 Homework 4 due in lecture on Thursday March 4 Consider two loudspeakers emitting sound waves of the same amplitude and wavelength of 15m and an observer located in the x y plane with the two loudspeakers being at 2m 0 and 2m 0 respectively and the observer being at 0 3m initially i Suppose the intensity of the combined sound heard by the observer is same as that of the sound from each loudspeaker by itself Determine the possible values of the inherent phase difference between the two sound waves ii The observer then moves along the x direction to reach the point 2m 3m For each of the possible cases mentioned in part i determine whether the interference at this new location of the observer is maximum constructive or maximum destructive or something in between 6 Homework 5 due in lecture on Thursday March 25 10 grams of oxygen gas at an initial pressure of 2 5 atm and a temperature of 25 C undergoes an isochoric cooling until the pressure is halved a What is the temperature at the end of the process b How much work has been done in this step Next the gas is isothermally compressed to its original pressure c What is the volume at the end of the compression d How much work has been done in this step Finally the gas undergoes an isobaric expansion to its original volume 2 e How much work has been done in this step f Show the full 3 step process on a p V diagram 7 Homework 6 due in lecture on Thursday April 1 A iron block of mass 10 g at some initial temperature and 10 g of ice at an initial temperature of 40 C are added to 1 g of water which is initially at 20 C This system is then allowed to reach thermal equilibrium Specific heats of ice water and iron are 2090 J kg K 4190 J kg K and 449 J kg K respectively and heat of fusion of water is 3 33 105 J kg i If the initial temperature of the iron block is 1000 C then what is the equilibrium temperature of this system ii Calculate the maximum intial temperature of the iron block such that the equilibrium temperature is not above 0 C iii Calculate the minimum intial temperature of the iron block such that the equilibrium temperature is not below 0 C 8 Homework 7 due in lecture on Thursday April 8 An ice making machine inside a refrigerator operates in a Carnot cycle It takes heat from liquid water at 0 0 C and rejects heat to a room at a temperature of 22 3 C Suppose that liquid water with a mass of 74 8 kg at 0 0 C is converted to ice at the same temperature Take the heat of fusion for water to be Lf 3 34 105 J kg A How much heat QH is rejected to the room Express your answer in joules to four significant figures B How much energy in joules must be supplied to the device 9 Homework 8 due in lecture on Thursday April 15 Two point charges are placed on the x axis The first charge q1 8 00 nC is placed a distance 16 0 m from the origin along the positive x axis the second charge q2 6 00 nC is placed a distance 9 00 m from the origin along the negative x axis A Calculate the electric field in terms of x and y components at point A located at coordinates 0 m 12 0 m An unknown additional charge q3 is now placed at point B located at coordinates 0 m 15 0 m B Find the magnitude and sign of q3 needed to make the total electric field …
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