**Explain the first condition for equilibrium.**

Difficulty: Medium

**The first condition of equilibrium:**

** **A body is said to satisfy the first condition of equilibrium if the resultant of all the forces acting on it is zero.

**Explanation:**

Let n number of forces F_{1}, F_{2}, F_{3},…………., F_{n }is acting on a body such that

F_{1}+F_{2}+F_{3}+……….+F_{n } = 0

Or

∑ F= 0……………. (1)

The symbol ∑ is a Greek letter called Sigma used for summation. Equation (1)

Is called the first condition of equilibrium.

The first condition of equilibrium can also be stated in terms of the x and y components.

F_{1x}+F_{2x}+F_{3x}.....+F_{nx} =0

And

F_{1y}+F_{2y}+F_{3y}.....+F_{ny} =0

Or

∑ Fx = 0

And

∑ Fy = 0

**Examples****:**

A book lying on the table or a picture hanging on the wall, is at rest and thus satisfies the first condition of equilibrium and is thus in equilibrium.

A paratrooper coming down with terminal velocity (constant velocity) also satisfies the first condition for equilibrium and is thus in equilibrium.

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