Answer
In experiment (f) when the applied force down the wall is $P = 18~N$, the block will move down the wall.
Work Step by Step
We can find the maximum possible force of static friction:
$F_f = (60~N)(0.55) = 33~N$
The block will move down the wall when the sum of the applied force $P$ directed down the wall and the block's weight is greater than $F_f$.
We can find the required magnitude of $P$ directed down the wall:
$mg+P \gt F_f$
$22~N+P \gt 33~N$
$P \gt 11~N$
In experiment (f) when the applied force down the wall is $P = 18~N$, the block will move down the wall.
