When the eraser is pressed on the blackboard (stationary) by hand, why is the pressure on the eraser not equal to the gravity?

When the eraser is pressed on the blackboard (stationary) by hand, why is the pressure on the eraser not equal to the gravity?

The pressure on the blackboard eraser is perpendicular to the blackboard, and the gravity is vertical downward

Hold a blackboard eraser (gravity 10N) with your hand, the other hand uses 10N force to pull the blackboard eraser downward without pulling it out, and then adds 10N force to just pull it out, asking black
What is the maximum static friction of the eraser?
Answer + analysis

Analysis of stress: vertical direction: downward gravity, tensile force and vertical upward static friction force. When it is just pulled out, the three forces are balanced, and the maximum static friction force is f = F + G = 20n + 10N = 30n

An object weighs 5N. Under which of the following conditions, does it receive 5N gravity?
A throws it horizontally, B puts it in the water, he floats on the water, C puts it on the high-speed train
I don't think it's easy to choose!

Both, as long as it doesn't take out the earth's surface, the mass remains unchanged, g = 9.8n/kg, and the gravity remains unchanged