A block is in contact with a rough surface as shown in the drawing. The block ha
ID: 2064187 • Letter: A
Question
A block is in contact with a rough surface as shown in the drawing. The block has a
rope attached to one side. Someone pulls the rope with a force , which is represented by the vector in the drawing. The force is directed at an angle with respect to the
horizontal direction. The magnitude of is equal to two times the magnitude of the
frictional force, which is designated f. For what value of is the net work on the block
equal to zero joules?
a) 0
b) 30
c) 45
d) 60
e) Net work will be done in the object for all values of theta
***Please show step by step how you got to the answer. Thanks***
Explanation / Answer
force F is applied at an angle with the horigental
F can be resolved into two rectangular components
Fcos in the -ve x-direction
Fsin in the +ve Y -direction
frictinal force is acting on the block in the +ve x-direction F=2f
the work done on the block will be zero if net force acting on it is zero
F=0
Fcos=f
2fcos=f
cos=1/2
=600
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