how does friction acts when we are writing with a chalk in blackboard?

When we write on a blackboard then static friction acts in between chalk and the surface of the board. When we push the chalk with little force then the chalk does not move, here the chalk does not move because the applied force is balanced by the static frictional force. But as soon as we apply greater force the chalk moves. It is because, the static friction is a self -adjusting force, that is why when we increase the applied force the chalk starts moving and we able to write. It is because, after certain limit the static friction will no longer be able to resist the applied and then the chalk will start to move.

So, the resisting force acts in between chalk and blackboard when we write something.

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It works like like brake.

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