# Why does the total sum of forces acting on a system always have to be equal to zero?

Why does the total sum of forces acting on a system always have to be equal to zero?

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Why does the total sum of forces acting on a system always have to be equal to zero?

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Hi!

The total sum of forces acting on a system is equal to zero only if it is not accelerating i.e. it is in a static equilibrium. This is a consequence of the conservation of linear momentum law.