The structure that holds the monitor plus the shelf up experiences tension or stretching. It has to be strong enough to withstand this force, making sure that the net force is 0 N. If the net force was not 0, the shelf would either push up the monitor or it would slowly topple down: The monitor would fall.
A structure that has to withstand structural tension is called a tie. Snapping is what happens when tension surpasses an object's ability to handle the lengthening force. |