Answer:
The minimum tension required in the cable in order for the log to begin to move is

Step-by-step explanation:
In this problem we use Newton's equations, put a system of reference centered in the log (as a punctual mass), and analyse the forces in vertical y and horizontal x directions.
We get that

for y, where N is the normal force, T is what we want to know and W is given in the problem, for x we have

where we have replaced N from the first equation, then we clear T

which is the answer to the problem.