Help in working this problem out please. Diagram from left shows pivot point, plank, box on top of plank. Underneath a block with an upwards arrow.

No jokes about planks please!

Centre of pivot point (left hand side of plank) plus attatched plank, length = 80cm. Box on extreme right hand side of plank. Underneath plank there is a block 20cm from centre of the pivot which has an upwards force of 100N.

Questions

Calculate the moment (turning affect) of the 100N force about the pivot? Show your working?

The box on the right hand side of the plank is just heavy enough to keep the plank balanced.
What is the moment of the box about the pivot. Give the units?
What is the weight of the box?

The 100N force acts on a block with area 5cm squared.
Calculate the pressure on the block? Give the units?

If anyone can work this out please show workings as well?

Much appreciated

Red Eye.