Boat Statics, Mastering phyics problem.

1. Oct 8, 2006

kenau_reveas

Information given:

boat owner pulls her boat into the dock shown, where there are six capstans to which to tie the boat. She has three ropes. She can tie the boat from the boat's center (A) to any of the capstans (B through G) along the dotted arrows shown.

Suppose the owner has tied three ropes: one rope runs to A from B, another to A from D, and a final rope from A to F. The ropes are tied such that F_{\rm AB} = F_{\rm AD}.

Extra Information given:

The following notation is used in this problem: When a question refers to, for example, F_AB_vec, this quantity is taken to mean the force acting on the boat due to the rope running to A from B, while F_AB is the magnitude of that force.

Question:

What is the magnitude of the force provided by the third rope, in terms of theta?

F_{\rm AB}\cos(\theta)
2 F_{\rm AB}\cos(\theta)
2 F_{\rm AB}\sin(\theta)
F_{\rm AB}\sin(\theta)

2. Feb 17, 2011

Photonjohn

2 F_{\rm AB}\cos(\theta) is the answer