How Can Friction Have Two Directions in Finding Tension?

[thoradicus]

Homework Statement

http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Mathematics%20%289709%29/9709_w11_qp_43.pdf
number 6, find 2 tension

Homework Equations

F=μR

The Attempt at a Solution

Okay, so R(reaction force)=Tcos30 Tsin30=F+20
the first tension is found, 68.5.

However, I am not understanding how there can be two tensions, as a result of frictions of 2 directions?? the marking scheme says the other friction is to prevent downward motion, but the tension isn't even downwards? How can there be 2 Tensions at the same time

 

[Doc Al]

However, I am not understanding how there can be two tensions, as a result of frictions of 2 directions?? the marking scheme says the other friction is to prevent downward motion, but the tension isn't even downwards?

The friction can act upwards or downwards, depending on how hard the string pulls.

If the ring is on the verge of sliding up, the friction acts down; on the verge of sliding down, the friction acts up. Friction always opposes slipping between surfaces.