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The two trees in the figure are 6.2 m apart. A back-packer s trying to lift his

ID: 1466717 • Letter: T

Question

The two trees in the figure are 6.2 m apart. A back-packer s trying to lift his pack out of the reach of bears Calculate the magnitude of the force F that he must exert downward to hold a 16-kg backpack so that the rope sags at its midpoint by 1.4 m. Ignore the friction between the rope and the branch on the left. Express your answer using two significant figures. Calculate the magnitude of the force F that he must exert downward to hold a 16-kg backpack so that the rope sags at its midpoint by 0.15 m. Express your answer using two significant figures.

Explanation / Answer

in equilibrium

Fnet = 0


angle made by rope with horizantal


theta = tan^-1(y/x ) = tan^-1(1.4/3.2) = 23.6

along vertical

2*F*sintheta = m*g

2*F*sin23.6 = 16*9.8

F = 195.8 N


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part(B

in equilibrium

Fnet = 0


angle made by rope with horizantal


theta = tan^-1(y/x ) = tan^-1(0.15/3.2) = 2.68

along vertical

2*F*sintheta = m*g

2*F*sin2.68 = 16*9.8

F = 1676.7 N