# 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 �, 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 = �Q/Mg B) E = Mg/�Q C) E = �Mg/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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