Three point charges, two positive and one negative, each having a magnitude of 20 ?C are placed at the vertices of an equilateral triangle (30 cm on a side). What is the magnitude of the electrostatic force on one of the positive charges?
A. 69 N
B. 40 N
C. 80 N
D. 57 N
E. 20 N
Answer: B
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A particle moves east at constant velocity v r for a time interval ?T. It then moves north at a constant velocity, with the same speed as before, for another time interval ?T. Finally it moves east again with the original velocity. At the instant an additional time interval ?T has elapsed, which of the following are true about the average velocity and the average acceleration for the motion described?
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Significant Figures: To get to her physics class, Alice walks 0.25 mi to the bus stop. She takes the bus 1.2 mi to the train station. She takes the train 13 mi and walks the remaining 0.17 mi to her class. How far is her commute expressed to the correct number of significant figures?
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