Identical point charges (+30 ?C) are placed at the corners of a rectangle (4.0 m × 6.0 m). How much external energy is required to bring a charge of 55 ?C from infinity to the midpoint of one of the 6.0-m long sides of the rectangle?
a. 22 J
b. 16 J
c. 13 J
d. 19 J
e. 8.0 J
b
You might also like to view...
A 4.00 kg mass is located at (2.00 m, 2.00 m, 0.00 m) and a 3.00 kg mass is located at (–1.0 m, 3.00 m, 0.00 m). If this system of masses rotated about the X-axis perpendicular to the Z-Y plane, then the moment of inertia of this system is
A. 24 kg 
B. 36 kg
C. 43 kg
D. 56 kg
E. 62 kg
A super train is moving along a track at a speed close to the speed of light. You are watching the train from the ground. You observe lightning to strike in two places along the track, a mile apart, at precisely the same time
What would someone on the train say? A) The two bolts of lightning struck at different times, and they struck at places that are more than a mile apart. B) The two bolts of lightning struck at the same time, and they struck at places that are less than a mile apart. C) The two bolts of lightning struck at different times, and they struck at places that are precisely a mile apart. D) The two bolts of lightning struck at different times, and they struck at places that are less than a mile apart.
Two balls, A and B, of mass m and 2m respectively, are carried to height h at constant velocity, but B rises twice as fast as A. The work the gravitational force does on B is
a. one quarter the work done on A. b. one half the work done on A. c. the same as the work done on A. d. twice the work done on A. e. four times the work done on A.
The oldest-known smelted iron dates to approximately what year?
(a) 27,000 BCE (b) 6000 BCE (c) 2500 BCE (d) 1000 BCE