online assignment 6-3-1

online assignment 6-3-1 - MasteringPhysics: Assignment...

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Manage this Assignment: 5. Magnetism Due: 11:00pm on Thursday, February 11, 2010 Note: To understand how points are awarded, read your instructor's Grading Policy . Print Version with Answers Mass Spectrometer Conceptual Questions Description: Short conceptual problem on uranium and carbon ion trajectories in the presence of a magnetic field. A beam of singly ionized uranium atoms ( and ) is injected into the mass spectrometer shown in the figure. The ions all have the same velocities and charges. The ions follow the trajectory illustrated. Part A Will the ions strike the collecting plate above, below, or at the same location as the ions? Hint A.1 Description of a mass spectrometer In a mass spectrometer, charged particles are injected into a region of uniform magnetic field (all with the same speed), where they travel along circular trajectories and, in this example, are collected after completing one-half of a complete circular orbit. If different mass isotopes are injected, they will trace different paths and be collected at different locations. Hint A.2 Dependence of radius on other parameters Once inside the spectrometer, the particles are acted on by a magnetic force and they trace circular paths. Applying Newton’s second law to their motion results in the equation . In our scenario, the velocity and field vectors are perpendicular, so . Also, since the particle moves along a circular path, the acceleration must equal the expression for centripetal acceleration: Page 1 of 16 MasteringPhysics: Assignment Print View 2/10/2010 http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1335164

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. This can be solved for the radius to yield . The diameter of their path, which is the distance from the opening of the spectrometer to their “landing spot” on the collecting plate is therefore . Thus, the position on the collecting plate is directly proportional to the mass of the particle. ANSWER: above below same location Part B If the magnetic field strength in the spectrometer is increased, will the spacing between where the and ions strike increase, decrease, or stay the same? Hint B.1 Spacing The relationship describes the diameter of any one particle's path in terms of the other parameters in the system. If two different isotopes are injected, the difference in their diameters is the spacing that appears on the collecting plate: , , . Thus, the spacing is proportional to the mass difference and velocity of the isotopes and inversely proportional to the field strength in the spectrometer. ANSWER: increase Page 2 of 16 MasteringPhysics: Assignment Print View 2/10/2010 http://session.masteringphysics.com/myct/assignmentPrint?assignmentID=1335164
decrease stay the same Part C If the initial velocity of the ions as they enter the spectrometer is increased, will the spacing between where the and ions strike increase, decrease, or stay the same? ANSWER:

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This note was uploaded on 07/01/2010 for the course PHYS 101213 taught by Professor Bratton during the Spring '10 term at CSU Chico.

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online assignment 6-3-1 - MasteringPhysics: Assignment...

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