Look around you, and you see a world at rest. The monitor, desk, and chair—and the building that contains them—are in a state described as static equilibrium. Indeed, it is the fundamental objective of many branches of engineering to maintain this state in spite of the presence of obvious forces imposed by gravity and static loads or the more unpredictable forces from wind and earthquakes.
http://session.masteringphysics.com/problemAsset/1007460/27/55544.jpg
As an example, consider the case of a board of length L and negligible mass. Take the x axis to be the horizontal axis along the board and the y axis to be the vertical axis perpendicular to the board. A mass of weight W is strapped to the board a distance x from the left-hand end. This is a static equilibrium problem, and a good first step is to write down the equation for the sum of all the forces in the y direction since the only nonzero forces of "Sigma F_net" that exist are in the y direction.
What is "Sigma F_y"? Your equation for the net force in the y direction on the board should contain all the forces acting vertically on the board.
Express your answer in terms of the weight W and the tensions in the two vertical ropes at the left and right ends T_l and T_r. Recall that positive forces point upward.
http://session.masteringphysics.com/problemAsset/1007460/27/55544.jpg
As an example, consider the case of a board of length L and negligible mass. Take the x axis to be the horizontal axis along the board and the y axis to be the vertical axis perpendicular to the board. A mass of weight W is strapped to the board a distance x from the left-hand end. This is a static equilibrium problem, and a good first step is to write down the equation for the sum of all the forces in the y direction since the only nonzero forces of "Sigma F_net" that exist are in the y direction.
What is "Sigma F_y"? Your equation for the net force in the y direction on the board should contain all the forces acting vertically on the board.
Express your answer in terms of the weight W and the tensions in the two vertical ropes at the left and right ends T_l and T_r. Recall that positive forces point upward.