The wings of birds produce lift in much the same way as an airplane wing. Unlike airplane wings, birds can flap their wings to produce forward movement and some lift.
Sometimes wings are used to create a downward force. Race cars often have an upside-down wing known as a spoiler mounted on the rear of the car. The downward force created by the spoiler pushes the tires down onto the road, giving the car better traction. Increased traction allows the car to go around corners at higher speeds.
Spray Bottles
Figure 9 shows the design of a typical hose-end sprayer. This type of sprayer is often used to apply fertilizers and pesticides to lawns, plants, and trees. A concentrated solution of the chemical that is to be sprayed is placed in the solution chamber. The sprayer is then attached to a garden hose.
Figure 9 The design of a hoseend sprayer is based on Bernoulli's principle. Pressure differences draw the concentrated solution up into the fast-moving water stream.
dAs water streams through the sprayer, it passes over the top of a small tube that reaches down into the solution chamber. The fast-moving water creates a low-pressure area at the top of the tube. The pressure difference between the solution chamber and the tube forces the concentrated solution up the tube. The solution then mixes with the water and is sprayed out of the end of the sprayer.
Section 13.2 Assessment
Reviewing Concepts
Describe Pascal's principle in your own words.- How is a hydraulic system able to increase force?
- How are fluid speed and fluid pressure related?
- How does an airplane wing produce lift?
Critical Thinking
Predicting Water is nearly incompressible. Air is easily compressed. Predict what will happen when an air-filled balloon is pulled to the bottom of a swimming pool.
Applying Concepts The area of an output piston is 25 times greater than the area of the input piston. If the input force is 40 newtons, what is the output force?
Relating Cause and Effect Two table tennis balls are suspended from strings so they hang at the same height with a small space between them. When a hair dryer is used to blow air between the two balls, the balls come together and touch. Explain why this occurs.
Inferring When cars pass one another in opposite directions on the highway, they tend to be forced together. Use Bernoulli's principle to explain why this happens.
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