Wednesday

October 22, 2014

October 22, 2014

Posted by **zoe** on Saturday, December 1, 2012 at 3:47pm.

- physics -
**Damon**, Saturday, December 1, 2012 at 8:19pmBuoyancy = 1000 kg/m^3 * 9.81 * vol

weight = 600 kg/m^3 * 9.81 * vol

net force up = 400 * 9.81 * vol

F = m a

400 * 9.81 * vol = 600 * vol * a

a = (2/3) * 9.81

--------------------------------

work done in rise to surface

= F * 10 = 4000*9.81*vol

= Kinetic energy on exit from water

= (1/2) m v^2

= .5 * 600 * vol * v^2

so

300 v^2 = 4000* 9.81

v^2 = 130.8

v = 11.4 m/s initial speed up

Ke = Pe at stop = m g h

but oh. I did not have to do that

work done during rise = m g h directly

4000*9.81*vol = 600*vol*9.81 * h

h = (40/6) = 6 3/3 m

note g did not matter in part b

NOte also that this problem ignores the force required to accelerate the water around the sphere. This "added mass" is actually comparable to the mass of water displaced by the sphere. I bet the text writer did not even know that (hydrodymanics, not usually covered in school or college physics but very important if you are designing fishing gear)

- physics -
**zoe**, Sunday, December 2, 2012 at 2:03pmwhy is work done during the rise= mgh directly?

**Answer this Question**

**Related Questions**

Physics - A cylinder shaped buoy is stationary out on a lake. The height of the ...

Physics - Archimedes principle. The weight of the bouy is given, so the weight ...

physics - A lobsterman's buoy is a solid wooden cylinder of radius r and mass M...

physics - A buoy oscillates in simple harmonic motion according to the motion of...

physics - A buoy oscillates in simple harmonic motion according to the motion of...

physics - A hollow steel buoy in thee form of a sphere of radius 0.5m is fixed ...

Precalc - I am having trouble figuring out this question Jan observes a buoy ...

Physics - You are on a boat heading out to sea. The boat is going 5m/s toward a ...

math - The angle of elevation from a buoy to the top of a bridge is 19 degrees. ...

Physics: Kinematics - A speed boat moving at 33.7 m/s approaches a no-wake buoy ...