Explore the interactive titled “Lift and Drag” under the Lift and Drag terms sec

Question

Explore the interactive titled “Lift and Drag” under the Lift and Drag terms section of the Science corner. You can also view it at http://www.pbs.org/wgbh/nova/space/lift-drag.html. Next, describe the way in which one could use both Newton's Third Law of Motion and the Bernoulli Effect to explain the generation of a lifting force when air passes over an airfoil. Read the article titled “Why don’t I fall out when a roller coaster goes upside down?” under the Forces terms section of the Science corner. You can also view it at http://www.loc.gov/rr/scitech/mysteries/rollercoaster.html. Next, imagine that you are trying to convince your apprehensive friend John to take his first roller-coaster ride. Then, explain to John the manner in which the roller-coaster engineers use physics to create a safe, yet thrilling ride. Note: In your explanation, be sure to include a discussion of potential energy, kinetic energy, angular momentum, frictional forces, and inertia when analyzing all aspects of the roller-coaster ride. Give an example of how you experience each of Newton’s three laws in your everyday life. Next, choose an example that hasn't already been mentioned in your textbook or by your classmates.

Explanation / Answer

“Lift and Drag”

At least 2 forces combine to cause lift:

As an airfoil moves, its shape and angle force oncoming air to curve as it passes the airfoil's top side. Because of this curve, the air above the foil moves farther and faster than air flowing underneath, as the speed of air increases, its pressure drops. This is called the bernoulli effect, the curved airflow generates more pressure below the airfoil than above and the airfoil is pushed upward

An airfoil also creates lift by bending or redirecting airflow, oncoming air follows the curved shape of the foil, shifting downward as it moves past, this downward motion causes an opposing force that pushes the airfoil up (newton's 3rd law)

“Why don’t I fall out when a roller coaster goes upside down?”

The climb up the first hill is accomplished by a lift or cable that pulls the train up. This builds up a supply of potential energy that will be used to go down the hill as the train is pulled by gravity. Then, all of that stored energy is released as kinetic energy which is what will get the train to go up the next hill. So, as the train travels up and down hills, its motion is constantly shifting between potential and kinetic energy. According to Newton’s First Law of Motion, “an object in motion tends to stay in motion, unless another force acts against it.” Wind resistance or the wheels along the track are forces that work to slow down the train. So toward the end of the ride, the hills tend to be lower because the coaster has less energy to get up them.

When you go around a turn, you feel pushed against the outside of the car. This force is centripetal force and helps keep you in your seat.

In the loop-the-loop upside down design, it’s inertia that keeps you in your seat. Inertia is the force that presses your body to the outside of the loop as the train spins around. Although gravity is pulling you toward the earth, at the very top the acceleration force is stronger than gravity and is pulling upwards, thus counteracting gravity.

Example of newton's 3 laws:

1st law: When starting a car it tries to move backwards (it is trying to keep its rest state so it doesn't moves forward at the first time)

2nd law: Free fall object or moving objects (let's exclude very small and very big objects such as atoms and planets) the forces acting on an object are propotional to its acceleration by a factor equal to its mass

3rd law: hugging a friend. The contact force between you and your friend while hugging has an equal an opposite counterpart in your friend's body

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