# Finding magnitude of the tension of a cord

1. Dec 14, 2009

### schyuler2

1. The problem statement, all variables and given/known data
A 20kg block is held in equilibrium by two massless cords, A, B. A is attached to the wall and B is attached to the ceiling. Find the magnitudes of the tensions of the cords.

Visual: http://i758.photobucket.com/albums/xx228/schuyler2_va/untitled.jpg?t=1260816320

2. Relevant equations
$$\Sigma$$ Forces = m*a

Normal force = mg(cos $$\theta$$)

3. The attempt at a solution
$$\Sigma$$ Forces = Tension of A + Tension of B + W + N
Tensions+Weight = ma

N = mg(cos $$theta$$)
W = 0
Tension A =?
Tension B=?

^not sure how to find the magnitudes

2. Dec 14, 2009

### PhanthomJay

There isn't any normal force in this problem, just gravity and tension forces. Why do you say W=0 when it is given that the block has a mass of 20 kG? And since the block is in equilibrium, sum of forces is 0, because a is 0. When you sum forces, look in the x and y directions separately, or else the problem becomes vectorially overwhelming. Note that the upper cord has an x and y component of tension, while the horizontall cord has a horizontal component only.