Static Equilibrium and Torque Homework Question

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SUMMARY

The discussion centers on a static equilibrium problem involving a hiker and a uniform bridge. The hiker weighs 985 N and the bridge weighs 3610 N, supported at both ends. The calculated forces exerted by the concrete supports are 2590 N at the near end and 2010 N at the far end. The solution involves using torque equations and verifying results through summation of vertical forces.

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Homework Statement



A hiker, who weighs 985 N is strolling through the woods and crosses a small horizontal bridge. the bridge is uniform, weighs 3610 N, and rests on two concrete supports, one at each end. he stops one - fifth of the way along the bridge. What is the magnitude of the force that a concrete support exerts on the bridge:

a) at the near end and
b) at the far end

Answer to a) 2590, b) 2010

Homework Equations



Static Equilibrium: ƩT = 0
T = Frsinθ


The Attempt at a Solution



Took opposite support as pivot point such that Fn x r is the CCW torque where r is the length of bridge
Expressed distance from the pivot point of each force in terms of r
Wrote net torque equation, crossed out r from both sides
Solved for Fn

a) Fn = 985 x 4/5 + 3610 x 1/2
Fn = 2593 N
b) Fn = 985 x 1/5 + 3610 x 1/2
Fn = 2002 N

I am not sure whether or not my approach to this problem is correct.
 
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Yes, looks good.
You can also sum the vertical forces - total must be zero - as a check.
2593 rounds to 2590, but I don't see how to get 2010 from 2002.
 
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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