Finding magnitude of the tension of a cord

[schyuler2]

Homework Statement

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

Homework Equations

$$\Sigma$$ Forces = m*a

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

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

 

[PhanthomJay]

Homework Statement

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

Homework Equations

$$\Sigma$$ Forces = m*a

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

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

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.

 

[kerimek]

of the tensions without knowing the angles of the cords or the distance from the wall/ceiling to the block. The equations used to solve for tension (such as \Sigma Forces = Tension + Weight) require knowledge of the angles and distances in order to accurately find the tensions. Without this information, it is not possible to accurately determine the magnitudes of the tensions. More information is needed in order to solve this problem.