Newton's law of motion

คํานํา หนังสอื อเิ ลก็ ทรอนกิ สเ ลม นจ้ี ัดทาํ ข้นึ เพอ่ื เปนสวนหนึ่งของวิชาวทิ ยาการคาํ นวณ(ว31191) เพือ่ ใหไดศึกษาความรูในเร่อื งกฎการเคลื่อนทขี่ องนิวตัน โดยประกอบไปดวย กฎการเคล่ือนท่ีของนวิ ตนั ประวตั ิของเซอรไอแซก นิวตนั กฎการเคลอ่ื นทีข่ อ ท่ี 1 กฎการเคล่อื นทข่ี อท่ี 2 และกฎการเคลื่อนทขี่ อที่ 3 ผูจ ดั ทําหวงั วาหนงั สืออิเลก็ ทรอนิกสเ ลมนจ้ี ะเปน ประโยชนก ับผอู าน หากมีขอ แนะนาํหรอื ขอผิดพลาดประการใด ผูจดั ทําขอนอมรบั ไวและขออภยั มา ณ ที่นด้ี วย ผจู ัดทํา 7 สงิ หาคม 2561

สารบัน หนา 1Sir Isaac Newton 2Newton's laws of motion 3First law of motion 4Second law of motion 5Third Law of Motion

1 Sir Isaac NewtonSir Isaac Newton was one of the greatest scientists and mathematicians that everlived. He was born in England on December 25, 1643. He was born the same yearthat Galileo died. He lived for 85 years.Isaac Newton was raised by his grandmother. He attended Free Grammar Schooland then went on to Trinity College Cambridge. Newton worked his way throughcollege. While at college he became interested in math, physics, and astronomy.Newton received both a bachelors and masters degree.While Newton was in college he was writing his ideas in a journal. Newton had newideas about motion, which he called his three laws of motion. He also had ideasabout gravity, the diffraction of light, and forces. Newton's ideas were so good thatQueen Anne knighted him in 1705. His accomplishments laid the foundations formodern science and revolutionized the world. Sir Isaac Newton died in 1727.

2 Newton's laws of motion Newton's laws of motion are three physical laws that, together, laidthe foundation for classical mechanics. They describe the relationship between abody and the forces acting upon it, and its motion in response to those forces. Moreprecisely, the first law defines the force qualitatively, the second law offers aquantitative measure of the force, and the third asserts that a single isolated forcedoesn't exist. The three laws of motion were first compiled by Isaac Newton in hisPhilosophiæ Naturalis Principia Mathematical (Mathematical Principles of NaturalPhilosophy), first published in 1687.[4] Newton used them to explain and investigatethe motion of many physical objects and systems.[5] For example, in the thirdvolume of the text, Newton showed that these laws of motion, combined with hislaw of universal gravitation, explained Kepler's laws of planetary motion.

3 First law of motionAn object at rest will remain at rest unless acted on by an unbalancedforce. An object in motion continues in motion with the same speedand in the same direction unless acted upon by an unbalanced force.This law is often called \"the law of inertia\".What does this mean?This means that there is a natural tendency of objects to keep on doing whatthey're doing. All objects resist changes in their state of motion. In the absence ofan unbalanced force, an object in motion will maintain this state of motion.ExampleThere are many excellent examples of Newton's first law involving aerodynamics.The motion of an airplane when the pilot changes the throttle setting of the engineis described by the first law. The motion of a ball falling down through theatmosphere, or a model rocket being launched up into the atmosphere are bothexamples of Newton's first law. The motion of a kite when the wind changes canalso be described by the first law. We have created separate pages which describeeach of these examples in more detail to help you understand this importantphysical principle.

4 Second law of motionAcceleration is produced when a force acts on a mass. The greater themass (of the object being accelerated) the greater the amount of forceneeded (to accelerate the object).What does this mean?Everyone unconsciously knows the Second Law. Everyone knows that heavier objectsrequire more force to move the same distance as lighter objects. However, theSecond Law gives us an exact relationship between force, mass, and acceleration. Itcan be expressed as a mathematical equation: F=ma or FORCE = MASS times ACCELERATIONExampleMike's car, which weighs 1,000 kg, is out of gas. Mike is trying to push the car to a gasstation, and he makes the car go 0.05 m/s/s. Using Newton's Second Law, you cancompute how much force Mike is applying to the car. F = 1,000 x 0.05 F = 50 newton Answer is 50 newton

5 Third Law of MotionFor every action there is an equal and opposite re-action.What does this mean?This means that for every force there is a reaction force that is equal in size, butopposite in direction. That is to say that whenever an object pushes another object itgets pushed back in the opposite direction equally hard.ExampleTwo skaters push against each other. The first skater on the left exerts anormal force N12 on the second skater directed towards the right, and thesecond skater exerts a normal force N21 on the first skater directedtowards the left.The magnitudes of both forces are equal, but they have oppositedirections, as dictated by Newton's third law.

6Third Law of MotionGravityThe action-reaction law also applies to the force of gravity, especially combined withNewton's Law of Dynamics. If you jump off a ladder, the force of gravity will pull youto the Earth according to F = mg, where m is your mass and g is the acceleration dueto gravity.But that same force is working in an opposite direction on the Earth, pulling it towardyou according to F = MG, where M is the mass of the Earth and G is its acceleration.Since the mass of the Earth is so much greater than your mass, its movement isextremely small.