Kite string force, negative or positive>

[2clients]

Homework Statement

A kite string exerts a 12-lb pull (|F|) on a kite and makes a 45 degree angle with the horizontal. Find the horizontal and vertical components of F.

Homework Equations

Pythagorean

The Attempt at a Solution

12*sqrt(2) for both horizontal and negative

My question is whether to assign a positive or negative to either value? It seems that either could work with the limited assumptions in the question? Or would it be more appropriate for the y force to be negative?

 

[Galadirith]

Hi 2clients, well actually this really does depend. When you have a taught string, as we have in your question, there is a tension in the string. Now this tension can be model as acting in both direction along the string. Imagine for example you help a piece of sting in your hands and pulled both ends, there is a force stopping both hands move further apart when the string is taught, so there must be a force acting on you right had to the left, and you left hand to the right :D

So what you need to ask is in which direction do you want the tension to be acting for the purpose of you question. In the question its says it exerts a pull on the kite, so the tension will be acting down the sting towards the person holding the sting, acting away from the kite, so it will have a negative y value and and may have a negative or positive x value depending on where the person is standing relative to the kite :D

That all said, most question wouldn't ask you to work out negatives and posatives, and they will simply want to know the magnitude of a force or the magnitude of its components, which are always positive :-) hope that helped

ps sorry if you knew most of that already, obviously I don't know what you already know :D

 

[thomate1]

I would say that the horizontal and vertical components of the force are both positive. This is because the force is exerted in the direction of the kite's motion, which is upwards and to the right at a 45 degree angle. The negative sign in the equation may have been used to indicate that the force is acting in the opposite direction of the positive x and y axes, but it does not necessarily mean that the force itself is negative. In this case, the force is positive in both magnitude and direction.