The graph in the figure shows the variation of the electric potential V(x) (in arbitrary units) as a function of the position x
(also in arbitrary units). Which of the choices below correctly describes the orientation of the x-component of the electric field along the x-axis?
A. Ex is positive from x = -2 to x = 0, and negative from x = 0 to x = 2.
B. Ex is negative from x = -2 to x = 0, and positive from x = 0 to x = 2.
C. Ex is negative from x = -2 to x = 2.
D. Ex is positive from x = -2 to x = 2.
A. Ex is positive from x = -2 to x = 0, and negative from x = 0 to x = 2.
B. Ex is negative from x = -2 to x = 0, and positive from x = 0 to x = 2.
C. Ex is negative from x = -2 to x = 2.
D. Ex is positive from x = -2 to x = 2.
1 answer:
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Answer:
B) A stack of books is carried at waist level across a room
Explanation:
Work is defined as:
where
F is the force applied
d is the displacement of the object
is the angle between the direction of the force and of the displacement
From the formula, we see that the work done is zero when the force and the displacement are perpendicular to each other. Let's now analyze each situation:
A) A bookcase is slid across carpeting. --> work is done, because the force that pushes the bookcase is in the same direction of the displacement
B) A stack of books is carried at waist level across a room. --> no work is done, because the force to carry the book is vertical, while the displacement of the books is horizontal
C) A chair is lifted vertically with respect to the floor. --> work is done, because the force that lifts the chair is vertical, and the displacement is vertical as well
D) A table is dropped onto the ground. --> work is done, because the force of gravity (that makes the table falling down) is vertical and the displacement of the table is also vertical.
Answer:
a) , b)
, c)
Explanation:
a) The net flux through the cube is:
b) The flux through the right face is:
c) The flux through the left face is: