SOLUTION: Please help? (Multiple Choice) A 9.6 kg box is held at rest by two ropes that form 30° angles with the vertical. An external force F acts vertically downward on the box. The fo

Question 1162039: Please help? (Multiple Choice)
A 9.6 kg box is held at rest by two ropes that form 30° angles with the vertical. An external force F acts vertically downward on the box. The force exerted by each of the two ropes is denoted by T. The force F is adjusted so that the magnitude of force T is equal to the weight w. The magnitude of force F, for which this occurs, is closest to:
A) 81 N
B) 78 N
C) 75 N
D) 72 N
E) 69 N

Answer by ikleyn(52847) (Show Source): You can put this solution on YOUR website!
.


Vertical component of the force T is  .


The sum of vertical components of the force T exerted to two ropes is  .


Since the magnitude of T is equal to the weight w,  the sum of vertical components of the force T  exerted to two ropes is .


The "box is held at rest" means that


     F + w = ,


It implies that


    F =  -  =  =  =  = 68.75 N.



ANSWER.  The closest option is E).

Solved, explained and answered.

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