# Past Exam for PHYS 1120 - GENERAL PHYSICS 2 with Lewandowski at Colorado (CU)

## Exam Information

 Material Type: Final Professor: Lewandowski Class: PHYS 1120 - GENERAL PHYSICS 2 Subject: Physics University: University of Colorado - Boulder Term: Fall 2007 Keywords: ImmediatelyConcentratedPerspectiveRectangularArrangementLoop CurrentAntiparallelOrientationMagnetic EnergyTotal Charge

## Sample Document Text

Phys 11120, page 1 Final Exam solutions - Physics 1120 - Fall, 2007 1. A balloon of mass M has been positively charged ( its charge is +Q) and is held up to the ceiling. The ceiling polarizes, so the balloon sticks to it. The friction coefficient between the balloon and the ceiling is µ, and we will assume that the electric field, E, created by the ceiling is uniform and directed upwards. What is the (minimum) magnitude E of this electric field? A) E = µQ/Mg B) E = Mg/µQ C) E = µMg/Q D) E = Q/Mg E) E = Mg/Q The upward force would be F=QE, the downward force is just Mg. Those are the only forces acting in the vertical direction. (Friction is horizontal, and thus totally irrelevant for this question!) QE = Mg means E = Mg/Q. The next two questions refer to this situation: Two positively charged particles, labeled 1 and 2, are placed a distance R apart in empty space and are released from rest. Particle 1 has mass m and charge +Q; particle 2 has mass ...

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