What is the Resultant Force of Tensions in Two Fishing Lines?

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To find the resultant force of tensions in two fishing lines with tensions of 20N and 30N at a 30-degree angle, the cosine rule is applied. The triangle of forces is set up with sides representing the tensions and the angle between them. The calculation yields a resultant force expression of 10√(6√3 + 13). However, the expected answer is given as 10√7, leading to confusion regarding the discrepancy. The discussion emphasizes the importance of correctly applying the cosine rule to resolve the resultant force accurately.
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Homework Statement


Two fishing lines hook onto one fish. The tensions in the lines are 20N and 30N, the angle between them being 30 degrees. Use a triangle of forces to find the magnitude of the resultant force of the tensions.


Homework Equations


cosine rule a^2 = b^2 +c^2 -2cbcos(theta)


The Attempt at a Solution



Triangle gives b=20, c = 30 and theta = 150.

Solving Resultant = 10root(6root(3) +13)


ANSWER IS GIVEN AS 10root(7), don't know how they get to this.
 
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dan2xtermart said:
Solving Resultant = 10root(6root(3) +13)
Your answer is correct.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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