Question

The resultant of two force. 3P and 2P is R. If the first force is doubled, then the resultant also doubled.
The angle between the two forces is
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Answer 1

Answer:

120

Step-by-step explanation:

Solve two equation :R

2

=9P

2

+4P

2

+12P

2

cosθ=13P

2

+12P

2

cosθ .....(1)

(2R)

2

=(2×3P)

2

+4P

2

+24P

2

cosθ=40P

2

+24P

2

cosθ ....(2)

Multiplying (1) by 4, 4R

2

=52P

2

+48P

2

cosθ .....(3)

Equating (2) and (3)

40P

2

+24P

2

cosθ=52P

2

+48P

2

cosθ

⇒12P

2

=−24P

2

cosθ

⇒cosθ=−

2

1

=cos120

∘

⇒θ=120

∘