Exam 6: Fluids and Motion

You are on an airplane trip to the islands for vacation. Your first flight is on a propeller driven airplane. The air flowing toward the spinning propeller blades doesn't slow down before it encounters those blades. Your second flight is on a turbofan-driven jet airplane. The air flowing toward the spinning fan blades slows down significantly before it encounters those blades. The air's pressure just before it encounters the turbofan's fan blades is

Reliving the "good old days" several physics faculty decide to spend a warm balmy summer's day squirting each other with garden hoses right in front of the physics building. They place their thumb over the end of the hose, and the water squirts out very quickly, because their thumb increases

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.

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

The four things that affect the amount of water flowing through a hose are

Briefly discuss four properties of a fluid that determine whether it exhibits turbulent or laminar flow.

As air flows through the horizontal ductwork in a warehouse, it passes through a fan inside the duct and the air's total energy increases. Since the air's speed doesn't change as the result of going through the fan, you know that the air's

On a windy day you notice that a tall light pole is bent away from its equilibrium position. If the wind speed were to increase the pole would

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

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.

When you blow on a pinwheel, it starts to spin. Even when you aim the air directly toward the wheel's pivot you produce a torque on the wing-like blades and they undergo angular acceleration. This torque is produced by

A curve ball in baseball curves because of

When a flat flounder moves rapidly, touching the level bottom of the ocean, what forces act on it and what is the net vertical force?

Suppose your instructor staggers into class after a week - long science lab equipment convention. She proceeds to explain Magnus lift in the following way. She has you consider a ball thrown to the left and spinning clockwise, having the wind velocity profile shown below. This is a "fastball" so it will rise, as correctly indicated. Please explain why the force F_m is inconsistent with the wind velocity profile.

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 fan can be used to circulate air around a room. The pressure at the inlet side of the fan is

When a fish hovers over the bottom of a lake, what forces act on it, and what is the net force?

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. -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?

You are taking a shower in your dormitory when someone flushes a toilet nearby. The pressure in the cold water line drops and you find yourself showering in what feels like molten lava. 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

Suppose you work in the E.R. and a choking patient comes in with their trachea half obstructed. (The diameter is half of what it was before the obstruction.) You manage to correct the problem and send them on their way safely, explaining that such obstructions are particularly dangerous because