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2.9: FORCES IN EQUILIBRIUM

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Forces in Equilibrium

When an object is in equilibrium, the

resultant force acting on it is zero. The object will either be

1. at rest

2. move with constant velocity.

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RESULTANT FORCEAsingle force thatrepresents the combinedeffect of two of more

forces in magnitude anddirection.

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Examples( Label the forces acted on the objects)

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Addition of Forces

Resultant force,

F = ____ + ____

Resultant force,

F = ____ + ____

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Using ruler and

protractor,draw the twoforces F1 and F2

from a point.

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STEP 2

Complete

theparallelogr

am

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STEP 3

Draw the

diagonal of theparallelogram.The diagonalrepresent theresultant force,F in magnitudeand direction.

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Resolution of Forces

Aforce F can be resolved into components which

areperpendicular to each other:(a) horizontal component , FX(b) vertical component, FY

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Resolution of Forces

Component of weightparallel to the plane

= mg sin

Component of weightnormal to the plane

= mg cos

Fx = F cos

Fy

= F sin