B O B B R O W NC H A P T E R 1 7

IN DEEP

SUMMARY

Bob Brown, a design engineer, explains:• the redesign process for a deep-water submarine named

Alvin.• How Alvin will explore deeper waters in remote regions to

get a glimpse into places that humans have never seen before.

• How Alvin will cope with extreme pressure environments

• The concept of buoyant force and how it affects the submarine’s movement.

• How a strong arm attached to Alvin will function as well as how it will benefit the team’s effort to research deeper water

RUBRIC

• 100%; 5 items+• 95%; 5 items• 85%; 4 items• 80%; 3 items• 75%; 2 items• 65%; 1 item• 60%; 0 item

PRESSURE• Pressure is defined as force per unit area

FLUIDS

• A fluid is a substance that flows easily, such as a liquid or a gas• When there is a fluid pressure difference, fluid will

flow from the area of higher fluid pressure to the area of lower

COMPRESSIBLE V. INCOMPRESSIBLE

• Compressible fluids occupy a smaller and smaller volume when under increasing pressure• Incompressible fluids do not change volume

under increasing pressure.• Liquids are nearly incompressible fluids.

HYDRAULIC SYSTEMS

• Hydraulic systems use liquid to transmit power by taking advantage of fluid characteristics and pressure changes.

WORK/ MECHANICAL ENERGY

• W=Fd – The work done on and object equals the force on the object times the distance traveled where “work” is defined as mechanical energy

QUESTION 1

Question• List three systems on the Alvin that Bob’s team is

planning to redesign for the Alvin’s replacement.Answer• The replacement of the structural system will be made

with titanium alloy to withstand the demanding pressure at its depth limit.

• The buoyancy system replacement will not use steel weights to submerge; rather, a system called Variable Ballast System (VBS) will be used to ascend and descend.

• Lastly, the new Alvin will be equipped with a robotic arm that can pick up rock, sediment, or marine life.

QUESTION 2

Question• How is the Alvin and example of the relationship

between engineers and scientists?Answer• Engineers design the technologies that allow scientists

to descend far deeper that any human could go, and to gather specimens of rock, sediment, or marine life for study.• The scientists and engineers apply their different

expertise to the goal of learning more about life in the extremely high-pressure environment of the deep ocean.

QUESTION 3

Question• Imagine that you’ve just inflated a kick ball and are

holding the air in the ball with your finger over the opening. What happens when you remove your finger and the air can pass freely through the opening? Explain in terms of pressure differences and fluid movement.

Answer• There is a pressure difference between the high

pressure inside the ball and lower-pressure atmospheric air. This difference will cause air to move rapidly from inside the ball to the outside until there is an equal amount of pressure inside and outside the ball.

QUESTION 4

Question• How is the compressibility of gasses used in a

designed system described in this chapter?Answer• The compressibility of gasses is used in the VBS.

Pushing water into the ballast tank compresses the air. The additional water reduces the sub’s buoyancy so it can dive. When the water is pumped back out, the air expands, increasing the buoyancy of the sub so it can resurface.

QUESTION 5

Question• How is the incompressibility of gasses used in a

designed system described in this chapter?Answer• The incompressibility of liquids is used in the

robotic arm. Increasing the pressure on one side of a working fluid in a hydraulic cylinder pushes on a piston, causing it to move. The piston is connected to one part of the robotic arm, causing it to move.