(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A block of wood weighs 50.0 N when weighed in air. A sinker is attached to the block, and the weight of the wood-sinker combination is 200 N when the sinker alone is immersed in water. Finally, the wood-sinker combination is completely immersed and the weight is 140 N. What is the density of the block?

2. Relevant equations

(I'm not so sure how to write out equations on here, being my first post, so bear with me...)

B=(rho)*V*g

SumF_y=0

(rho)=m/V

And that's really all I can come up with...

3. The attempt at a solution

I haven't been able to get a good start on this problem, but I think it will have to do with the buoyancy force-weight of the system=0. I'm really not sure on this one...

And the second question... I probably shouldn't expect anyone to waste this much time helping me, lol...

1. The problem statement, all variables and given/known data

A solid copper ball with a diameter of 3.00 m at sea level is placed at the bottom of the ocean, at a depth of 10.0 km. If the density of the seawater is 1030 kg/m^3, how much does the diameter of the ball decrease when it reaches bottom?

2. Relevant equations

(rho)=m/V

V_sphere=[4(pi)r^3]/3

P=P_o+(rho)gh

3. The attempt at a solution

P=1.01x10^5+(1030)(9.8)(1.0x10^4)

My problem is, how do I relate the pressure, P, to the density and volume of the ball?

I guess the majority of my problems are conceptual. I sometimes don't understand how to begin a problem, or which equations to use in order to find my variables. Does anyone have any good general tips for my situation? Thanks for looking, and I hope this isn't too much for someone to help me out with...

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# Two Questions on Archimedes's Principle

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