A ladder? You all might wonder. *shakes head. No wonder Mr Khoo never made it as an art teacher. Can anyone tell me, which part of the drawing looks like a ladder? Me, Justina and the rest were like laughing our asses off when he flashed this picture. Please shut out all your dirty thoughts, it looks like a cactus can? Or maybe an uneaten sausage that's been attack by god knows what.
Recalling lecture...
Mr Khoo was telling us that the ladder has a tendency to slide down. The friction experienced by the ladder would be represented by the arrow pointing upwards while the friction on the wall is the arrow pointing downwards(Newton's 3rd Law).
Aiyerrr, I don't know if I'm right or not. =/