physics 270-force presentation 04062015
TRANSCRIPT
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Force and Newton’s 3 Laws of Motion
Reginald Cruz| Illiana Aguirre| Physics 270
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What is Force and Newton’s 3 Laws of Motion? Today, we’re going to explain what Force is, Newton’s 3 Laws, and Gravity with Weight
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Force and Newton’s 3 Laws of Motion
• Force is anything that pulls or pushes an object. The amount of force to the object will change the motion of the object or prevent the object from chaning motion.
• Example: DragonBall Z throws a fireball at Chung-Li (Streetfighter) during a battle. The amount of force Z uses to throw the fireball can change the motion of where the fireball will hit, in this case, it will knock Chung-Li down to the ground on impact.
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Newton’s Three Laws of Motion
• Law of Inertia-Page 126: “A Body that is in motion continues in motion with the same velocity (at constant speed and in a straight line) and a body at rest continues to rest unless an unbalanced outside) force acts upon it”.
• Law of Acceleration-Page 128: “The total force acting on a body is equal to the mass of the body times its acceleration”.
• Law of Action and Reaction-Page 140: “For every force applied by object A to object B (action), there is an equal but opposite force exerted by object B to object A (reaction)”.
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Law of Inertia
Example
• A car moving on the road in motion will continue to move until it stops.
2nd example
• When riding a bus (like Muni or BART), also applies to Newton’s first law. The bus stops at a point in time, then it will stay at rest until it moves on.
Third example
• Walking from one point to another follows Newton’s first law.
• If you stop at a midpoint and rest, then you will stay at rest then use more velocity unless an unbalanced force acts upon it.
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Law of Acceleration (Newton’s 2nd Law)It states the total force acting on a body is
equal to the mass of the body times its acceleration.
The equation is F = ma where F is the total force, m = mass, and a = acceleration
Here’s how we would use it: Back to the first scenario on the battle between Dragonball Z and Chung-Li. What force is necessary for Chung-Li to throw a fireball back at Dragaonball Z if the mass (m) of the fireball is 1500 kg and the acceleration of the fireball is 100 m/s2.
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Solution
• First, we know m = 1500 kg and a = 100 m/s2 and F = ?
• The equation is F = (1500 kg)(100 m/s2)
• The amount of force is 150,000 kg m/s2 or 150,000 N (1 N = 1 kg m/s2) needed for her shot to hit Dragonball Z.
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Another example of Newton’s 2nd Law
• What is the acceleration of a ball being kicked by a force of 950 N applied to the mass of 900 kg?
• The Force = 950 N and Mass = 900 kg and a = ?
• To find the acceleration, F = ma a = F/m
• Then a = (950 N)/(900 kg)
• which a = (950 N)/(900 kg) * 1 kg m/s2/1 N
• The acceleration of the ball is 1.05 m/s2.
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Gravity and Weight
• The weight of an object is based on the amount of the gravitational pull exerted on an object by the earth.
• An example is if a satellite dish falls from space as it enters the earth’s atmosphere. The weight of the dish is being pulled by the gravity from earth.
• It also gives this equation (Section 5.3 Page 131): Fw = mg where Fw = the weight, m = mass, g = acceleration due to gravity, g = 9.80 m/s2 or g = 32.2 ft/s2.
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Problem Scenario involving Gravity and Weight
• What is the weight of a rock with a mass of 350 kg?
• Solution: m = 350 kg g = 9.80 m/s2 Fw = ?
• Fw = (350 kg)(9.80 m/s2) 3430 kg m/s2 or 3430 N (1 N = 1 kg m/s2)
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Works Cited
Ewen, Dale, Neill Schurter and Erik P Gundersen. Applied Physics . 10th Edition. Upper Saddle River: Peasrson Education Inc, 2012. textbook. 7 April 2015.