Identical point charges (+30 mC) 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 mC 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...
As the Universe cooled, it eventually reached a temperature of 3,000 K and protons were able to capture and hold electrons to form neutral hydrogen. This process is known as
a. ionization. b. isotropy. c. annihilation. d. recombination. e. hydration.
A Carnot cycle consists of
A) four adiabats. B) two adiabats and two isotherms. C) two isobars and two isotherms. D) two adiabats and two isobars. E) four isotherms.
Angular Momentum: A puck moves on a horizontal air table. It is attached to a string that passes through a hole in the center of the table. As the puck rotates about the hole, the string is pulled downward very slowly and shortens the radius of rotation, so the puck gradually spirals in towards the center. By what factor will the puck's angular speed have changed when the string's length has decreased to one-half of its original length?
A. 2
B. 4
C. 
D. 1
E. 1/2
Vision Problems: A farsighted person cannot see clearly objects that are closer to her eyes than 60.0 cm. Which one of the following combinations represents the correct focal length and the refractive power of the contact lenses that will enable her to comfortably see the objects at a distance of 25.0 cm from her eyes?
A. -42.9 cm, +2.33 diopters B. -42.9 cm, -2.33 diopters C. +42.9 cm, +2.33 diopters D. +42.9 cm, -2.33 diopters E. +60 cm, +42.9 diopters