Question

A traction device employing three pullets is applied to a broken leg as shown in the sketch. The middle pulley is attached to the sole of the foot and a mass m supplies the tension in the ropes. Find the vaule of the mass m (in kg) if the force exerted on the sole of the foot by the middle pulley is to be 150N. (round off answer to nearest whole number)

Answer 1

What is the angle between the ropes ??

Anyway, I got an idea what this question is asking.

Note that tension will be same throughout the rope.

The sine components of tension in upper and lower rope will cancel out.

Only horizontal components will be added up

Let angle be

so,

F = 2Tcos

where F = 150 N and T = mg

so,

F = 2mgcos

m = F / 2gcos

m = 150 / 2 * 9.8 * cos

just put the value of given in the question and solve for m....too easy.

Please, Let me know if you have any doubt ( its pretty simple and straight forward)