Calculating Pulley Forces: A Frustrating Problem

[kuany]

this is a simple pulley question but i can't seem to get it right
the person which i have very badly drawn weighs 80kg and I'm trying to calculate P.
This is wat I have done, please tell me wat I have done wrong.
1st i calculated T1:
80*9.81=784.8
T1= 784.8/2
=392.4
and to calculate T2:
T2= 392.4/2
= 196.2
and T2=P
but the answer says that P=157

Please help me I'm becoming very frustrated.
Thank you.

 

[brewnog]

For a start, your first step is wrong.

The chap is pulling on the rope too, - T1 isn't just half the force from the bosun's weight.

You've got the right idea though; tensions either side of the pulley being equal. Draw free body diagrams for each pulley, the bosun, and the support, and take it from there.

 

[haynewp]

The box he is sitting on has only one cable at the left end so the box would rotate under his weight, unless there is some other information you are not giving. Is the box supposed to be in the air or sitting on the ground?