Quiz 3 - Chapters 5/6 Problems
Tennis ball A is dry and fuzzy. Tennis ball B is wet, and the fuzz is matted down. What will happen when the two balls are hit horizontally so as to have the same initial horizontal velocity?
- A goes farther than B because the fuzz reduces drag.
Why does the handle of a metal spoon submerged in boiling soup feel hot?
- Heat from the soup is transferred through the spoon by conduction.
When a fluid is in steady - state flow and its path bends, the pressure on the outside of the bend is always
- Higher than the pressure on the inside of the bend.
Suppose you have gotten a new job where you have to design balls that fly through the air with as little resistance as possible. You know that in front of the ball there is laminar flow, so in back of the ball there should be
- Laminar flow, so the leading and trailing pressure environments are similar
A popular drink is composed by pouring several types of beverage (one on top of the other) in order to get a layering effect. In what order should the individual beverages be poured into the glass so that your drink is stable?
- Most dense first and then in order of decreasing density.
One of the many things that make an artery blockage dangerous is
- The amount of fluid passing through the blockage is proportional to the fourth power of the diameter of the opening
You are seated at a table in a Paris Café, contemplating life and watching the bubbles rise upward in your glass of carbonated water. You can think of many physical reasons why those carbon dioxide bubbles should rise upward through the water. Which of the follow observations is not true and therefore does not help explain why the bubbles rise in your Perrier?
- The pressure inside a bubble is much less than the pressure in the water around it.
Soil heats up much faster than water when the two are exposed to sunlight. Use that fact and your understanding of heat transfer to predict which way the wind will blow near the surface of the earth as the sun rises near the seashore.
- The surface wind will blow from the water toward the land.
Why are failures in dams more likely to occur closer to the bottom of the dam?
- Water pressure is higher at the bottom
As the Reynolds number increases,
- flow is going from being viscous dominated to inertia dominated and therefore turbulent
Taking a shower and sometime flushes the toilet. Pressure in cold water line drops and your shower water gets really hot. This loss of cold water pressure occurs when the toilet lets cold water flow through the pipes delivering it to the bathroom and the water's speed in those pipes increases. Assuming all the piping to be about on the same level, the cold water's faster motion in the delivery pipes reduces its pressure in the shower head because faster moving water
- has less pressure than slower moving water.
A stream of smoothly flowing water arcs through the air and hits the side window of a house. At the surface of the window, right where the stream of water hits it, the water's pressure is
- higher than atmospheric and the water's speed is slower than in the stream.
Flowing honey is less likely to become turbulent than flowing water because
- honey's large viscosity favors laminar flow.
You stop for a cappuccino at a coffee shop and notice that the tiny white bubbles of steamed milk remain on the surface of the coffee. These air-filled bubbles stay where they are, rather than descending into the coffee or rising into the air, because they are
- less dense than the coffee but more dense than the air above the coffee.
You are a mechanic in a garage and are working on a carburetor that is made of metal, has a glass inspection window and plastic gears for the choke. If all three types of material are at the same temperature and each type of material is in contact with the other two, then
- no heat will flow between any parts.
If a golf ball were smooth rather than dimpled, it would
- not travel as far after being hit by a golf club.
You run an old hose from the spigot behind your home, across your yard, and up the tree to a sink inside the tree house. You let water fill the hose all the way to the tree house sink and then leave the hose pressurized overnight, with no water flowing in it. Unfortunately, the hose cannot tolerate high pressure anymore and it springs a leak around midnight. By morning your whole backyard is a swamp. The most likely site for the leak is
- on the ground—the lowest point on the hose.
The top surface of a calm, smoothly flowing stream is always at atmospheric pressure. As water in this stream runs into a tree stump and slows almost to a stop, the water's top surface
- shifts upward slightly above the normal stream level.
You are filling a jar of honey from the spigot at the bottom of a large barrel at the grocery store. The honey flows extremely slowly, so the store manager has the barrel refilled. Now the honey flows much more rapidly from the spigot because
- the pressure of the honey at the bottom of the barrel increases as the height of honey in the barrel increases.
The four things that affect the amount of water flowing through a hose are
- water viscosity, hose length, inlet and outlet pressures and hose diameter.
Which temperature scale has 373 as the boiling point of water?
Kelvin
Wind is one of nature's ways of transferring energy through
convection
Aerodynamic forces consist of
drag and lift
A curve ball in baseball curves because of
lift forces
A pedestrian bridge crosses a street. This bridge is entirely supported by columns from below. A gap at each end of the bridge separates the bridge's surface from the sidewalks leading to the bridge. The width of each gap changes with time. This width is smallest
on hot days
Dimples on a golf ball hit without spin
reduces drag
Suppose you have an aquarium and you notice that you have a solid plastic decoration and a rock of about the same volume but twice as dense, and both are totally submerged in the water. The buoyant force on the plastic object is about ___________as that on the rock.
the same
The reason fast-moving water makes noise is
turbulence
