20. A box of mass m is pulled by a force F, which
makes an angle with the horizontal. A
frictional force fis applied on the box as it slides
on a horizontal surface, as shown in the figure
below. Which of the following represents the net
work on the box when it covers a distance d?
F
I
f+
A.
B.
C.
√ D.
E.
Fd
(F-f)d
F cos d
m
(F cos - f)d
(F sino-f)d
To
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