Determine the force in a pulley system

Zheng_ · Nov 14, 2016

Homework Statement

If A has a mass of 300kg, determine the mass of B if the system in figure P4-28 is to be in balance.
(What I couldn't understand is the 2T_b in the answer.)

Homework Equations

ΣF_y=0[/B]

The Attempt at a Solution

Since the pulley on top is connected with two pulley at the bottom, its force is doubled?

Handwritten free-body diagram labelled 4-28 of a pulley with upward forces 2T_B at the top and T_B on each side, a downward load of 300, and the equations sum Fy = 0, 4T_B = 300, T_B = 75 kg.

gneill · Nov 14, 2016

The middle pulley (above block B) has two tensions T_b pulling it downward (red string in figure below). So what must be the tension in the blue string?

Diagram of a pulley system hung from a ceiling, with a red string and a blue string running over three pulleys, and blocks labelled A and B hanging from the strings.

Determine the force in a pulley system

Homework Statement

Homework Equations

The Attempt at a Solution

Discussion

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