Reading Quiz 20 Key

Due 3:30 pm, Thursday, November 5th

Physics 105, Fall Term, 2009


Reading: Chapter 9.4-9.6

Did you complete the reading assignment?

Yes
No

KEY CONCEPTS:

1) Buoyant force replaces the normal force when an object rests on a fluid instead of a solid.

2) Archimedes' principle relates buoyant force to mass of displaced fluid.

Archimedes' principle states that an object submersed in a fluid (partially or completely), is buoyed up by a force which is equal to the weight of the fluid Go to: http://www.walter-fendt.de/ph11e/buoyforce.htm. The right side of the applet allows you to change a few of the parameters of the mass, spring, and liquid. The 'Measuring Range' option just changes what you can measure, change it to 2000 N now so that it will not limit anything else you do in the applet. You can also see the weight of the mass, how much volume of liquid is replaced, the buoyant force acting on the mass, and the force of tension from the spring scale at the right side of the applet.

Drag the mass into the water with the mouse. How are the buoyant force, weight of the mass, and measured force of tension in the spring scale related?

Now change the base area of the mass to 50 cm2 and the height to 10 cm so the mass has the same volume but a different shape. Does changing the shape of an object affect the buoyant force acting on it?

Yes
No

Now drag the mass so that only about half of it is submerged in the liquid. Does this change the buoyant force acting on the mass? Why or why not?

Submerge the entire mass again. Increase the density of the mass. How does this affect the buoyant force?

Increases buoyant force
Decreases buoyant force
Does not change buoyant force

Now increase the density of the fluid (keep it less than the density of the mass). How does this affect the buoyant force?

Increases buoyant force
Decreases buoyant force
Does not change buoyant force

Now make the density of the mass and fluid the same. How are the buoyant force, weight of the mass, and measured force of tension in the spring scale related when the densities of the fluid and mass are the same?


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Was there anything that you didn't understand in the reading assignment?  What was confusing to you?


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