Understanding Forces in a Simple Pulley: Explained with an Image

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In a simple pulley system, the upward forces acting on objects P and W are indeed due to tension in the rope. The downward force is the force of gravity acting on both objects. The tension force changes direction but does not alter the magnitude of the gravitational force. It is important to understand that the tension in the rope is what allows both objects to be lifted. This discussion highlights the relationship between tension and gravitational force in pulley systems.
AlbertE97
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As seen in the image below, a hand is pulling one end of a rope that is on a simple pulley, and the object W is pulling another end.

What I don't understand is what kind of force acts both objects P and W upward. The downward force is the force of gravity. Since I've learned that these kind of pulleys simply change the direction of the force, why shouldn't both the forces acting upward be equal to the mass of the other object times g?
(English my 2nd language)

fixed_pulley_36349_lg.gif
 
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Is P acting upward?

This seems like the time to perform a simple physical experiment.
 
Nevermind, I've just learned it is the Tension force.
 
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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