Exam 6: Fluids and Motion

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

Suppose you are operating a fan and it is stalling. One thing that would not prevent stalling would be to

The pressure in a water pipe may not necessarily be lower in regions where the water moves faster when

Aerodynamic forces consist of

You are out watering the lawn and your neighbor decides to strike up a conversation with you. She says that she bought an extra long hose because of all the factors that affect how much water travels through a hose, the length is clearly not one of them because the water is incompressible so what goes in equals what comes out. Please comment on the scientific accuracy of her statement.

Which of the following would cause a household fan to stall?

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 it traveled faster. The object that experienced the larger amount of drag is

The top surface of a calm, smoothly flowing stream is always at atmospheric pressure. As water in this stream suddenly speeds up, the water's top surface

A squirt gun is a simple type of water pump in which a plunger attached to the trigger forces water out of a nozzle and across the room. When you squeeze the trigger of the gun, water squirts out of the nozzle because

When a Frisbee is flying horizontally through the air, the speed of the air flowing over the Frisbee's top is

At what place in or near the jet engine is gas moving the fastest relative to the flying airplane?

Suppose you are a teacher and, to your excitement, the local weather person comes for a classroom visit! She is talking about tornadoes and says that there is air moving very rapidly upwards through the funnel and air moving at the same speed outside the funnel. Such motion would cause

Suppose your instructor staggers into class after a week - long physics joke convention. She proceeds to explain drag in the following way. She has you consider a ball thrown to the left, having the wind velocity profile shown below. She goes on to say that the air is compressed in front of the ball and rarefied behind it, so there is air pressure pushing backwards, which is exactly drag. Is the picture shown consistent with her explanation?

Dimples on a golf ball hit without spin

An airplane pilot must be very careful to maintain a proper angle of attack during flight because

The onset of turbulent flow happens for a Reynolds number of about

If a golf ball were smooth rather than dimpled, it would

Surface roughness help golf and tennis balls travel with less drag, but yet objects that travel under water (submarines by human design and animals by natural design) generally have streamlined, smooth surfaces. Please explain such a difference.

Consider a baseball thrown to the left, spinning clockwise and experiencing laminar flow as shown in the picture below. Based upon the wind speed experienced at the top and bottom of the ball, comment on whether or not this would account for the ball's obtaining a lift (the vertical component of the purple arrow) from spinning. Also, mention whether the ball shown is a good candidate for the Magnus force or for wake deflection.

When you pour honey into a bowl, it flows smoothly. If you did the same with water, it would splash. These different behaviors occur because honey's high