Name: __________________________ Date: _____________



1.
The pressure in a water pipe is always lower in regions where the water moves faster only when
A.
the pipe increases in altitude towards the faster fluid end
B.
the pipe is level.
C.
anything other than water is in the pipe
D.
the pipe is made of plastic


2.
Flowing honey is less likely to become turbulent than flowing water because
A.
honey's large density favors laminar flow.
B.
water's large viscosity favors turbulent flow.
C.
water's large pressure favors turbulent flow.
D.
honey's large viscosity favors laminar flow.


3.
To set the world land speed record and travel faster than the speed of sound, the Thrust SSC vehicle used two jet engines that produced about a 250,000 horsepower. The principal reason why this car needed so much power to travel so fast is that
A.
a car's momentum is proportional to its power, so reaching very high momentum requires very high power.
B.
the pressure drag on a car increases dramatically as the car's speed increases.
C.
the force of the car's momentum was enormous and the jet engines were needed to supply that force.
D.
Newton's second law requires a very fast moving object to have a very large acceleration and thus a very large force.


4.
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
A.
the pressure of the honey at the bottom of the barrel increases as the height of honey in the barrel increases.
B.
the density of the honey decreases as the height of the honey in the barrel increases.
C.
the viscosity of the honey decreases as the height of honey in the barrel increases.
D.
the viscosity of the honey increases as the height of honey in the barrel increases.


5.
As the Reynolds number increases,
A.
flow is becoming more laminar.
B.
flow is going from being viscous dominated to inertia dominated and therefore turbulent.
C.
flow is slowing down.
D.
flow is speeding up.


6.
You have just set up a weather station for your daughter to observe wind speeds at home. You had to move it up from the ground because when it was too close to the ground the wind speed readings are all too small. This is because
A.
The air near the ground is too dense to move well.
B.
The ground is hot so air movement there is always upward, never sideways.
C.
The boundary layer of a moving fluid moves slower than at other points farther into the fluid.
D.
Someone kept stepping on the wind speed gauge.


7.
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.
B goes farther than A due to the extra weight of the water.
B.
B goes farther than A due to the smoother surface.
C.
A goes farther than B because the fuzz reduces drag.
D.
Both go the same distance.


8.
You are at the park throwing a stick for your dog to fetch. When you throw a smooth straight stick by one end, it tends to tumble end over end as it flies through the air. However, when you throw a stick that still has some leaves attached to one end, it flies through the air without tumbling and travels in a smooth arc with the stick leading and the leaves trailing. This automatic alignment occurs because
A.
the center of mass of the stick is no longer near its geometric center.
B.
the center of pressure is at the same point as the center of mass in the stick, stabilizing its flight.
C.
the viscosity of the air near the leaves is highest, producing torques which oppose any rotation the stick had after leaving your hand.
D.
the drag forces acting on the leafy stick are not uniform around the stick's center of mass.


9.
Why does fuzz on a tennis ball help it travel farther when hit?
A.
The fuzz causes turbulence on the leading edge of the ball only.
B.
The fuzz causes turbulence on the trailing edge of the ball only.
C.
The fuzz “trips the boundary layer, causing turbulence everywhere around the ball..
D.
The fuzz causes laminar flow everywhere.


10.
Suppose that we are able to send astronauts to Mars and they engage in a game of golf on the red planet's surface. Given that the atmosphere on Mars is considerably less dense than our own, how will the path of the ball be affected?
A.
There is less drag and gravity, so the ball will go further than if there were air.
B.
There is less lift, so the ball doesn't go as far than if there were air.
C.
Less air means lower gravity, so it will go further than if there were air.
D.
There is no significant effect.


11.
Dimples on a golf ball hit without spin
A.
result in purely laminar flow.
B.
increase drag.
C.
reduce drag.
D.
are merely decorative.


12.
If a golf ball were smooth rather than dimpled, it would
A.
travel much too far after being hit by a golf club.
B.
curve toward the left after being hit by the club of a right-handed golfer.
C.
curve toward the right after being hit by the club of a right-handed golfer.
D.
not travel as far after being hit by a golf club.


13.
You have two golf balls that differ only in their surfaces. One has dimples, while the other is smooth. Which ball has a greater pressure difference between the leading and trailing edges?
A.
The pressure difference is greater for the smooth ball.
B.
The pressure difference is greater for the dimpled ball.
C.
The pressures are exactly the same.
D.
there is no leading or trailing pressures.


14.
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
A.
Turbulent flow, because there will be lower density.
B.
Turbulent flow, because there will be less drag.
C.
Laminar flow, so the leading and trailing pressure environments are similar.
D.
No air flow at all.


15.
Suppose you are practicing baseball and throw the ball with a spin so that it moves forward and curves to the right. Now when the actual game takes place you are pitching with the wind behind you. Please explain how you could alter your throw so as to make the ball take the same path.

Answer:


16.
In some motion pictures, airplane passengers are sucked out of the plane when a door is opened and the airplane is in flight. Comment on whether such an effect is scientifically realistic or not.

Answer:


17.
You are out for a bicycle ride on a calm, windless day. You are heading northward on a level road and are experiencing a pressure drag force that pushes you toward the south. This air resistance explains why you have to keep pedaling to maintain your constant speed. If someone were to examine the air that you have left behind you after you have passed through it, they would find that the air's velocity is
A.
zero everywhere.
B.
straight northward everywhere.
C.
zero on average but that it is swirling rapidly in all directions.
D.
straight southward everywhere.


18.
When a Frisbee is flying horizontally through the air, the speed of the air flowing over the Frisbee's top is
A.
higher than the speed of the air beneath it and the pressure on top of the Frisbee is greater than the pressure beneath it.
B.
lower than the speed of the air beneath it and the pressure on top of the Frisbee is less than the pressure beneath it.
C.
lower than the speed of the air beneath it and the pressure on top of the Frisbee is greater than the pressure beneath it.
D.
higher than the speed of the air beneath it and the pressure on top of the Frisbee is less than the pressure beneath it.


19.
You are holding two identical-looking balloons, one filled with air and one filled with water. You drop these two balloons from a very tall bridge and notice that the water-filled balloon hits the ground first because its terminal velocity is larger. The terminal velocity of the water balloon is larger than that of air balloon because
A.
conservation of momentum requires the lighter air-filled balloon to travel more slowly.
B.
although the drag forces on the two equally shaped balloons are the same, the buoyant force on the air balloon is larger so the net force on that balloon is smaller and it falls more slowly.
C.
the larger force of gravity on the water balloon must be balanced by a larger drag force, which occurs at a higher speed.
D.
although the force of gravity on the two balloons is the same, the water balloon has more inertia and travels downward more quickly.


20.
When a fish hovers over the bottom of a lake, what forces act on it, and what is the net force?
A.
Lift only, for a net force up.
B.
Lift only, for a net force zero.
C.
Lift and weight, for a net force up.
D.
Lift and weight, for a net force zero.


21.
In old western movies, after having fired their guns people would blow across the end of their guns and smoke would come out the barrel. Please explain.

Answer:


22.
Please consider the funnel of a tornado which holds its size (radius) and therefore its rotation rate. Now imagine that the funnel is made up of many tiny particles moving around in circles. You are examining one of those particles, which represents a tiny portion of the funnel cloud. You may ignore gravity for this problem.

a) Please identify the direction of the net force acting on one of the particles.
b) Why would it make sense if we said that air is moving very rapidly up through the center of the funnel and almost stationary outside the funnel for it to remain in uniform circular motion?

Answer:


23.
Suppose you are in a car and you fixed one of the windows using a plastic bag. As you drive down the highway fairly rapidly would you expect the bag to bow outwards away from you, bow inwards towards you or do nothing? Please explain.

Answer:


24.
An airplane pilot must be very careful to maintain a proper angle of attack during flight because
A.
too low an angle of attack will cause the Bernoulli effect to be pre-empted and hence the plane will never take off.
B.
too steep an angle of attack will cause to much energy to be wasted in frictin with the air via laminar flow.
C.
too low an angle of attack will cause turbulent flow around the wing and hence stalling.
D.
too steep an angle of attack will cause turbulent flow around the wing and hence stalling.


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