How Do You Calculate the Tension in Cables Suspending a Loudspeaker?

[circuscircus]

Homework Statement

A 20kg loudspeaker is suspended 2 m below the ceiling by two 3m long cables that angle outward at equal angles. What is the tension in the cables?

Homework Equations

The Attempt at a Solution

cos theta = 2/3, theta=48.2 degrees
w=mg=20kg * 9.8m/s^2 = 196N

But the answer is 147N

 

[Hootenanny]

Try drawing a FBD and see what the forces tell you.

 

[stewartcs]

w=mg=20kg * 9.8m/s^2 = 196N

You have to break this problem down into components in order to solve it.

Hint: Since the angles are the same, the tension in both cables will be the same.