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Transcript of Air resistance is a form of friction that acts to slow down any object moving in the air. Air...
![Page 1: Air resistance is a form of friction that acts to slow down any object moving in the air. Air resistance is a force that gets larger as an object moves.](https://reader036.fdocuments.in/reader036/viewer/2022062515/56649cc25503460f94989c67/html5/thumbnails/1.jpg)
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• Air resistance is a form of friction that acts to slow down any object moving in the air.
• Air resistance is a force that gets larger as an object moves faster.
• Air resistance also depends on the shape of an object.
Air Resistance: a.k.a. Fluid Friction
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• When an object falls, it speeds up as gravity pulls it downward.
• At the same time, the force of air resistance pushing up on the object is increasing as the object moves faster. • Finally, the upward air resistance force becomes large enough to equal the downward force of gravity!
Fluid Friction, continued
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• When the air resistance force up equals the gravitational force down (weight), the net force on the object is zero. • So According to Newton’s laws of motion, the object’s acceleration would be zero, and its speed no longer increases.
Fluid Friction, continued
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Terminal Velocity• Terminal Velocity is
the maximum speed an object travels when falling (e.g. “terminal” meaning: END)
• Terminal velocity is reached when the object no longer accelerates, but is traveling at a constant speed because the force of air resistance pushing up balances the force of gravity pulling down.
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• Sometimes forces and motion are not in a straight line.
Projectile Motion
• When throwing an object, the horizontal force from the throw propels the object forward while the gravitational force pulls the object downward. • The net force thus acts at an angle to the direction the object is moving, and so the object follows a curved path.
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Projectile Motion, continued
• Projectile motion is the curved path an object follows when thrown or propelled forward. It has BOTH a horizontal force AND vertical force component.
• Examples: shooting a basketball, a leaping frog, a catapult, aiming at a target.
• The faster an object is thrown, the farther it travels before gravity pulls it to Earth.
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• CIRCULAR MOTION is the motion of an object in a circle.
• If you are in circular motion, your direction of motion is constantly changing, thus the object is accelerating.
Circular Motion
• If an object is constantly accelerating, there must be a force acting on the object the entire time.
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Circular Motion, continued
• Opposing inertia is a force called centripetal force which pulls an object inward toward the center of the circle.
• In circular motion the centripetal force is always perpendicular to the forward motion.
• Due to inertia, your body wants to propel forward in a straight line as the merry-go-round turns.
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• Gravity is an attractive force that pulls objects toward each other.
• Gravity depends on the mass of the objects and the distance between them.• The gravitational force stronger: larger objects; closer objects
Gravitational Force
• The gravitational force weaker: smaller objects; farther away objects
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• Only Earth is close enough and massive enough to exert a noticeable gravitational force on you.
• The force of gravity between you and Earth is about 1,650 times greater than between you and the Sun.
Gravitational Force, continued
• The force of gravity causes all objects near Earth’s surface to fall with an acceleration of 9.8 m/s².
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Satellite Motion • Satellites go
around Earth in nearly circular orbits, with the centripetal force being gravity.
• A satellite’s motion is like that of a baseball, gravity pulls inward toward the earth and inertia causes the object to continue moving forward.
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Satellite Motion
• The speed at which an object must move to go into orbit near Earth’s surface is about 8 km/s, or about 29,000 km/h. HAVE YOU EVER SEEN A SATELLITE IN THE NIGHT SKY?
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________________ pulls an object inward toward the center of a circle.
A. Projectile MotionB. Satellite MotionC. Circular MotionD. Centripetal Force
Question 1
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Answer
The answer is D, “centripetal force.”
Question 1
________________ pulls an object inward toward the center of a circle.
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Describe how an object has curved motion.
Question 2
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Answer
Once an object is moving forward, inertia causes the object to continue forward. Centripetal force pulls the object inward. The two forces create a curved net force.
Describe how an object has curved motion.
Question 2
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Momentum• When two or more
objects interact, momentum may be exchanged, but the total amount of momentum does not change.
• Momentum is a measure of how difficult it is to stop a moving object. In other words, momentum in the strength of an objects motion.
• It equals the product of mass and velocity (p = mv)
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Calculations of Momentump = mv
• In this equation, p = momentum (kg ∙ m/s); m = mass (kg); and v = velocity (m/s)
• Calculate the momentum of a 14 kg bike traveling north at 2 m/s.
p = mv28 kg ∙ m/s northp = (14 kg)(2 m/s) =
p = ? m = 14kg v = 2m/s north
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Calculations of Momentump = mv
•A 10,000 kg train in traveling east at 15m/s. Calculate the momentum of the train.
p = mv
150,000 kg ∙ m/s east
p = (10,000 kg)(15 m/s) =
p = ? m = 10,000kg v = 15 m/s east
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Calculations of Momentump = mv
•What is the momentum of a car with a mass of 900 kg traveling south at 27 m/s?
p = mv
24,300 kg ∙ m/s south
p = (900 kg)(27 m/s) =
p = ? m = 900kg v = 27 m/s south
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In your own words, what is momentum?
Question 3
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Answer
• Momentum is a measure of how difficult it is to stop a moving object. In other words, momentum in the strength of an objects motion.
Question 3
In your own words, what is momentum?
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What is the formula for momentum?
Question 4
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Answer
p = mv (momentum = mass * velocity)
Question 4
What is the formula for momentum?