Ms. Beland



PHYSICS 2016-17November 10, 2016Today’s Agenda (Day 52)Housekeeping:Homework Check: Ch 8 Notes Class Activity: Catch Up Day: complete missing homework or begin Section 8.1 Practice ProblemsHOMEWORK: Read Ch 8 – Rotational MotionREMINDERS:Ch 8 Test Tuesday, Nov. 15Term Project: Go, Score, Win Nov. 23PHYSICS 2016-17Practice ProblemsPRACTICE PROBLEMS 8.1INSTRUCTIONS: Read the questions below. Show all work and calculations as appropriate.What is the angular displacement of each of the following hands of a clock in 1.00 h? State your answer in three significant digits.The second handThe minute handthe hour handA rotating toy above a baby’s crib makes one complete counterclockwise rotation in 1 min. What is its angular displacement in 3 min?What is the toy’s angular velocity in rad/min?If the toy is turned off, does it have positive or negative angular acceleration? Explain.If a truck has a linear acceleration of 1.85 m/s2 and the wheels have an angular acceleration of 5.23 rad/s2, what is the diameter of the truck’s wheels?The truck in the previous problem is towing a trailer with wheels that have a diameter of 48 cm. How does the linear acceleration of the trailer compare with that of the truck?How do the angular accelerations of the wheels of the trailer and the wheels of the truck compare?PRACTICE PROBLEMS 8.2If a torque of 55.0 N?m is required to turn a bolt and the largest force you can exert is 135 N, how long a lever arm must you use to turn the bolt?You have a 0.234 m long wrench. A job requires a torque of 32.4 N?m, and you can exert a force of 232 N.What is the smallest angle, with respect to the handle of the wrench, at which you can pull on the wrench and get the job done?A friend can exert 275 N. What is the smallest angle she can use to accomplish the job?You stand on a bicycle pedal, as shown in Figure 7 of p. 210 in your textbook. Your mass is 65 kg. If the pedal makes an angle of 35? above the horizontal and the pedal is 18 cm from the center of the chain ring, how much torque would you exert?Ashok, whose mass is 43 kg, sits 1.8 m from a pivot at the center of a seesaw. Steve, whose mass is 52 Kg, wants to seesaw with Ashok. How far from the center of the seesaw should Steve sit?A bicycle chain wheel has a radius of 7.70 cm. If the chain exerts a 35.0 N force on the wheel in the clockwise direction, what torque is needed to keep the wheel from turning?Two stationary baskets of fruit hang from strings going around pulleys of different diameters, as shown in Figure 10 of p. 213 in your textbook. What is the mass of basket A?Suppose the radius of the larger pulley in the question above is increased to 6.0 cm. What is the mass of basket A now?Two children of equal masses sit 0.3 m from the center of the seesaw. Assuming that their masses are much greater than that of the seesaw, by how much is the moment of inertia increased when they sit 0.6 m from the center? Ignore the moment of inertia for the seesaw.Suppose there are two balls with equal diameters and masses. One is solid, and the other is hollow, with all its mass distributed at its surface. Are the moments of inertia of the balls equal? If not, which is greater?Calculate the moments of inertia for each object below using the formulas in Table 2 of page 214 of your textbook. Each object has a radius of 2.0 m and a mass of 1.0 kg.A thin hoopA solid, uniform cylinderA solid, uniform sphereA solid wheel accelerates at 3.25 rad/s2 when a force of 4.5 N exerts a torque on it. If the wheel is replaced by a wheel which has all of its mass on the rim, the moment of inertia is given by I = mr2. If the same angular velocity were desired, what force should be exerted on the trap?A bicycle wheel on a repair bench can be accelerated either by pulling on the chain that is on the gear or by pulling on a string wrapped around the tire. The tire’s radius is 0.38 m, while the radius of the gear is 0.14 m. What force would you need to pull on the string to produce the same acceleration you obtained with a force of 15 N on the chain?A chain is wrapped around a pulley and pulled with a force of 16.0 N. The pulley has a radius of 0.20 m. The pulley’s rotational speed increase from 0.0 t0 17.0 rev/min in 5.00 s. What is the moment of inertia of the pulley?PRACTICE PROBLEMS 8.3What would be the forces exerted by the two sawhorses if the ladder in Example Problem 5, p. 223 of the textbook had a mass of 11.4 kg?A 7.3 kg ladder, 1.92 m long, rests on two sawhorses, as shown in Figure 20 of p. 223 of the textbook. Sawhorse A on the left, is located 0.30 m from the end and sawhorse B, on the right, is located 0.45 m from the other end. Choose the axis of rotation to be the center of mass of the ladder.What are the torques acting on the ladder?Write the equation for rotational equilibrium.Solve the equation for Fa in terms of Fg.How would the forces exerted by the two sawhorses change if A were moved very close to, but not directly under the center of mass?A 4.5 m long wooden plank with 24 kg mass is supported in two places. One support is directly under the center of the board and the other is at one end. What are the forces exerted by the two supports?PHYSICS 2016-17Term ProjectPROJECT: Go, Score, Win!DESCRIPTIONEach team will investigate a different sport, based on interest. Teams will identify major component motions within the chosen sport and assign one motion to each team member. Each individual team member will videotape the assigned/selected motion and complete a motion analysis. Team members may assist each other. The team uses the individually collected data and analyses to create a documentary video. The video must explain the physics applications involved in the sport and address how physics and knowledge of physics can be used to improve athletic performance. In the process, each team member becomes an "expert" on one motion. The team collaborates in order to identify common themes and patterns to highlight in their video. OBJECTIVES (Theory)Justify Newton’s Laws of Motion in terms of equilibrium and net force situationsAnalyze the motion of a projectilePERFORMANCE OBJECTIVESStudents will KNOW:Vocabulary and usage of the following terms: position, velocity, acceleration, slope, forceThe relationships shown by slope and area on graphsNewton’sStudents will be able to DO:Operate digital cameras to take still photos and videoConstruct and interpret motion graphsUtilize video analysis softwareAdd vectorsUse software to create moviesAnalyze forcesPredict the effect of variables on pathways of motionApply Newton’s Laws of Motion to sports and to projectile motionDRIVING QUESTIONHow can forces influence motion to give athletes the winning advantage in a sport?RUBRICSDocumentary Video Rubric (for Documentary Video product)Graphical Analysis Rubric (for Motion of a Toy Car analysis assignment)Addition of Forces Rubric (for Addition of Forces assignment)Projectile Motion Rubric (for Video Analysis of one motion of a particular sport)Reasoning Skills Rubric (for Video Analysis of one motion of a particular sport)Discussion Rubric (for overall project)PRODUCTSMajor Group Product: Documentary Video – showing how physics is involved and can be used for a competitive edge in a particular sportIntended to help coaches and athletes in particular sports to use physics to gain a competitive edgeMinor Individual Product:Task Management Chart (for Teams)Motion of a Toy Car (analysis practice) write-upAddition of Forces responseVideo analysis of one motion that is a component of a particular sportRESOURCES & MATERIALSTechnology Needed:Video cameras Digital cameras Video analysis software (optional) Video production software (e.g. Windows Movie Maker) Digital voice recorder (optional) Computers Optional Web Resources:SAS in School Web Inquiry 79: What are vectors and what is vector algebra in School Web Lesson 486: Projectile Motion SAS in School Web Resources 708: Internet Sites (related to force and motion) Vector tutorial Some Links for the Physics of Sports: Soccer Football Softball/Baseball Basketball into groups of four based on interest in a particular sport. Decide on the sport to be plete the Task Management Chart. At the initial meeting, teams should create a group contract, select 4 motions from your selected sport, and decide who will be responsible for the analysis of each plete the graphical analysis activity – The Motion of a Toy Car – and submit digitally (1 per group), according to due date.Individual students within their respective teams should videotape the selected motions of the particular sport. You will then need to create position-time graphs for these motions. To do this, play the video frame by frame, recording time from the video player software and measure distance from a reference point on the screen. Water soluble markers may be helpful. For either method, a means of determining scale is essential. There must be an object in the video that is physically measured to be used to convert video size to real-world size. This could be a piece of equipment ex: a baseball bat or a person’s height or other object in video. The created graphs should be analyzed and evaluated using the Graphical Analysis Rubric.You will need to complete individual video analysis of a motion.Create the documentary video.Students conduct a peer review of team products, using the documentary and Content Video Rubrics to evaluate your own video and those of other groups. Discuss suggestions for making the videos better.Make changes to the documentary video based on the critique. Finalize video. Present to classComplete Self-Reflection assignment.DUE DATESNovember 23, 2016 ................
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