1 PHYSICS 1101 Sample Quiz 3 This is a closed book, and closed notes problem. Calculators and software apps on your phone are permitted only to do mathematical calculations. The ONLY physics equations that may be used are those given below. Define all symbols and justify all mathematical expressions used. Make sure to state all assumptions used to solve a problem. Credit would be given for a well-communicated problem-solving framework based on correct physics. On a quiz, each problem is worth 25 points: In the context of a unified solution, credit will be awarded as follows: a useful picture including all relevant quantities, specifying the question, listing what is known, and giving the physics approach best suited to the problem is worth 9 points; useful physics diagrams and giving the equations corresponding to your physics approach using quantities defined by your picture or diagram is worth 5 points; planning the solution by describing how you could use the equations of your physics approach to construct an algebraic answer is worth 5 points; solving those equations for a symbolic result and checking the validity of that result is worth 4 points; calculating a numerical value with correct units and evaluating the validity of the numerical answer is worth 2 points. If no numerical answer is required, 1 point will be added to the planning the solution and 1 point to the solving the equations and checking the validity of the solution. Useful Mathematical Relationships: For a right triangle: sin q = ! " , cos q = # " , tan q = ! # , A = $ % ab a2 + b2 = c2, sin2 q + cos2 q = 1 For a circle: C = 2pR , A = pR2 For a sphere: If Ax2 + Bx + C = 0, x = Fundamental Concepts, Principles, and Definitions: = m V % F' = ma' v! #$% = x t a ! #$% = v! t KE = 1 2 mv & p' = mv' E'()#* E()(+(#* = E() E,-+ E+.#)/'%. = F#$% d = F#$% d = F 1 r p' '()#* p' ()(+(#* = p' () p' ,-+ Under Certain Conditions: Useful constants: 1 mile = 5280 ft, g = 9.8 m/s2 = 32 ft/s2 !" !#ABB " !! % F' = 0 % ' = 0 v! = x t a ! = v! t F = 2 N F / N F = kx F#$% = 1 2 kx E+.#)/'%. = F d = Fd E/3/+%4 = KE/3/+%4 + U/3/+%4 U/3/+%4 = mgh U/3/+%4 = 1 2 kx & !"# = a b c q , (a + b)& = a& + 2ab + b& V = & ' R' , S = 4R% f f f 2 3 Problems (2 individual & 1 group) each worth 25 points 1. You have been hired on the technical staff of a new mystery movie. In the movie, a body was discovered in a field during hunting season. One suspect is a hunter who was seen shooting their rifle horizontally in the same field around the time of the death. The hunter claims they shot at a deer and missed. You are working on the "flashback" scene that shows the hunter's version of firing their rifle with the bullet kicking up dirt where it hits the ground. Your job is to calculate the distance from the hunter that the bullet hits the ground based on the speed the bullet leaves the rifle (muzzle velocity), the mass of the bullet, and the rifle's height above the ground when it was fired. 2. At the train station, you notice a large horizontal spring at the end of the track where the train comes in. This is a safety device to stop the train so that it will not go plowing through the station if the engineer misjudges the stopping distance. While waiting, you wonder how fast a train could be going and still be stopped by the spring. You decide to calculate this speed as a function of the length of the spring, which you can measure. You also look up the mass of the train, the strength of the spring, and the coefficient of kinetic friction and the coefficient of static friction between the track and the train's wheels when the brakes are applied. 3. You are driving your car uphill along a straight road. Suddenly, you see a car run a red light and enter the intersection ahead of you. You slam on your brakes, missing the other car, and skid in a straight line along the road to a stop with skid marks 100 feet long. A policeman observes the incident and gives a ticket to the other car for running a red light. He also gives you a ticket for exceeding the speed limit of 30 mph. When you get home, you check the internet and estimate that the coefficient of kinetic friction between your tires and the road was 0.60, and the coefficient of static friction was 0.80. You estimate that the hill you were on made an angle of 10 o with the horizontal. In your owner's manual you find that your car weighs 2,050 lbs. Will you fight the traffic ticket in court?