02_Buoyancy.pdf

Physics 213R: Recitation

Buoyancy

 A maximum of three students is allowed per group. If a group of four students must be
formed, check with your recitation instructor before starting work on the activity.

 All the members of the group must participate in the activity. If a student is not participating
(even when present) s/he may receive a score of zero in the activity. Every student in the

group is expected to be able to fully explain the group’s work on this activity.
 Students arriving 10 minutes or more late will not be admitted.

 This activity must be returned at the end of the recitation period. All the students completing
the activity must be present when handing it to the recitation instructor; those absent may not

receive credit.

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integrity violation.

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it for you records. It will serve as evidence of your grade for this activity.

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mistakes to your recitation instructor within two weeks of completing the activity.

Date: ________________

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Problem text and figures © 2013 Pearson Education, Inc.

1. A rectangular wooden block of weight W floats with exactly one-half of its
volume below the waterline.

a. What is the buoyant force acting on the block?

i. 2W
ii. W

iii. W/2
iv. The buoyant force cannot be determined

b. The density of water is 1.00 g/cm
3
. What is the density of the block?

i. 2.00 g/cm
3

ii. between 1.00 and 2.00 g/cm
3

iii. 1.00 g/cm
3

iv. between 0.50 and 1.00 g/cm
3

v. 0.50 g/cm
3

vi. The density cannot be determined.

c. Masses are stacked on top of the block until the top of the block is level with the
waterline. This requires 20 g of mass. What is the mass of the wooden block?

i. 40 g
ii. 20 g

iii. 10 g

d. The wooden block is removed from the water bath and placed in an unknown
liquid. In this liquid, only one-third of the wooden block is submerged. Is the

unknown liquid more or less dense than water?

e. What is the density of the unknown liquid ρunknown? (Express your answer
numerically in grams per cubic centimeter.)

Problem text and figures © 2013 Pearson Education, Inc.

2. Glycerin is poured into an open U-shaped tube until the height in both sides is 20 cm.
Ethyl alcohol is then poured into one arm until the height of the alcohol column is 20 cm.

The two liquids do not mix. What is the difference in height between the top surface of

the glycerin and the top surface of the alcohol? Express your answer with the

appropriate units. (The density of glycerin is 1260 kg/m
3
; the density of ethyl alcohol is

790 kg/m
3
.)

3. Water flows from the pipe shown in the figure with a speed of 6.0 m/s.

a. What is the water pressure as it exits into the air? Express your answer to two

significant figures and include the appropriate units.

b. What is the height h of the standing column of water? Express your answer to
two significant figures and include the appropriate units.

Problem text and figures © 2013 Pearson Education, Inc.

4. The bottom of a steel “boat” is a 6.00m × 10.0m × 4.00cm piece of steel (ρsteel = 7900
kg/m

3
). The sides are made of 0.510 cm -thick steel. What minimum height must the

sides have for this boat to float in perfectly calm water (ρwater = 1000 kg/m
3
)? Express

your answer with the appropriate units.