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2.4 TWO FORCES ACTING ON A PARTICLE

In order to add two forces together, the ‘start’ of the second force needs to be moved to the ‘end’
of the first force, with the resultant going from the start of the first force directly to the end of the

second force (as shown in the diagram). This rule is then extended when considering more forces
and it is easier when applying the parallelogram method.

Figure 2.13: Two Forces Acting on a Particle

Example 2.3

The two forces P and Q acts on a bolt A as shown in Figure 2.13 (a). Determine the resultants.

Figure 2.14 (a)

Calculation
Given data

P = 40 N

Q = 60 N

Use law of cosines and law sines because the two sides and angle are known.

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