Newton was the only son of a prosperous local farmer, also named Isaac, who died three months before he was born. A premature baby born tiny and weak, Newton was not expected to survive. When he was 3 years old, his mother, Hannah Ayscough Newton, remarried a well-to-do minister, Barnabas Smith, and went to live with him, leaving young Newton with his maternal grandmother. The experience left an indelible imprint on Newton, later manifesting itself as an acute sense of insecurity. He anxiously obsessed over his published work, defending its merits with irrational behavior.
At age 12, Newton was reunited with his mother after her second husband died. She brought along her three small children from her second marriage. Newton was enrolled at the King's School in Grantham, a town in Lincolnshire, where he lodged with a local apothecary and was introduced to the fascinating world of chemistry. His mother pulled him out of school at age Her plan was to make him a farmer and have him tend the farm.
Newton failed miserably, as he found farming monotonous. Newton was soon sent back to King's School to finish his basic education. Perhaps sensing the young man's innate intellectual abilities, his uncle, a graduate of the University of Cambridge's Trinity College , persuaded Newton's mother to have him enter the university. Newton enrolled in a program similar to a work-study in , and subsequently waited on tables and took care of wealthier students' rooms.
When Newton arrived at Cambridge, the Scientific Revolution of the 17th century was already in full force. The heliocentric view of the universe—theorized by astronomers Nicolaus Copernicus and Johannes Kepler, and later refined by Galileo —was well known in most European academic circles. Yet, like most universities in Europe, Cambridge was steeped in Aristotelian philosophy and a view of nature resting on a geocentric view of the universe, dealing with nature in qualitative rather than quantitative terms.
During his first three years at Cambridge, Newton was taught the standard curriculum but was fascinated with the more advanced science.
All his spare time was spent reading from the modern philosophers. The result was a less-than-stellar performance, but one that is understandable, given his dual course of study. It was during this time that Newton kept a second set of notes, entitled "Quaestiones Quaedam Philosophicae" "Certain Philosophical Questions".
The "Quaestiones" reveal that Newton had discovered the new concept of nature that provided the framework for the Scientific Revolution. Though Newton graduated without honors or distinctions, his efforts won him the title of scholar and four years of financial support for future education.
In , the bubonic plague that was ravaging Europe had come to Cambridge, forcing the university to close. After a two-year hiatus, Newton returned to Cambridge in and was elected a minor fellow at Trinity College, as he was still not considered a standout scholar. In the ensuing years, his fortune improved. Newton received his Master of Arts degree in , before he was During this time, he came across Nicholas Mercator's published book on methods for dealing with infinite series.
Newton quickly wrote a treatise, De Analysi , expounding his own wider-ranging results. He shared this with friend and mentor Isaac Barrow, but didn't include his name as author. In August , Barrow identified its author to Collins as "Mr. Newton's work was brought to the attention of the mathematics community for the first time. Shortly afterward, Barrow resigned his Lucasian professorship at Cambridge, and Newton assumed the chair.
Newton made discoveries in optics, motion and mathematics. Newton theorized that white light was a composite of all colors of the spectrum, and that light was composed of particles. His momentous book on physics, Principia , contains information on nearly all of the essential concepts of physics except energy, ultimately helping him to explain the laws of motion and the theory of gravity. Along with mathematician Gottfried Wilhelm von Leibniz, Newton is credited for developing essential theories of calculus.
Newton's first major public scientific achievement was designing and constructing a reflecting telescope in As a professor at Cambridge, Newton was required to deliver an annual course of lectures and chose optics as his initial topic. He used his telescope to study optics and help prove his theory of light and color. The Royal Society asked for a demonstration of his reflecting telescope in , and the organization's interest encouraged Newton to publish his notes on light, optics and color in Sir Isaac Newton contemplates the force of gravity, as the famous story goes, on seeing an apple fall in his orchard, circa Between and , Newton returned home from Trinity College to pursue his private study, as school was closed due to the Great Plague.
Legend has it that, at this time, Newton experienced his famous inspiration of gravity with the falling apple. According to this common myth, Newton was sitting under an apple tree when a fruit fell and hit him on the head, inspiring him to suddenly come up with the theory of gravity.
While there is no evidence that the apple actually hit Newton on the head, he did see an apple fall from a tree, leading him to wonder why it fell straight down and not at an angle. Consequently, he began exploring the theories of motion and gravity. It was during this month hiatus as a student that Newton conceived many of his most important insights—including the method of infinitesimal calculus, the foundations for his theory of light and color, and the laws of planetary motion—that eventually led to the publication of his physics book Principia and his theory of gravity.
In , following 18 months of intense and effectively nonstop work, Newton published Philosophiae Naturalis Principia Mathematica Mathematical Principles of Natural Philosophy , most often known as Principia.
Principia is said to be the single most influential book on physics and possibly all of science. Its publication immediately raised Newton to international prominence.
The best method is to explain, ask a question, then check with the demo. For younger students there is no need to go into the math. Each tab contains a different method for presenting this demo as written by a former outreach student. This demonstration shows what [conservation of momentum] is. First off, does anyone know what momentum is encourage any response, right or wrong, and try to use them to lead to the next part?
That means the heavier something is or the faster it is moving, the more momentum it has. So which would have more momentum, a semi-truck going 50 miles an hour or a motorcycle going the same speed?
The useful thing about momentum is that it must be conserved. What that means is that if two things crash into one another we can use their combined momentum before the crash to predict what will happen after the collision. When I drop one of these balls with a mass of say one ball, it will have a set speed at the bottom.
When it collides with the other balls let the ball go it will push exactly one ball up at the same speed on the other side. Now that we know that, what will happen if I drop two balls together? What about 3? For fun I like to go through all the balls up to and including just swinging all of them as technically it still works and the kids usually laugh at that. Not only does this show us that momentum and energy must be conserved, but also that we can use our understanding of physics to predict what will happen!
This, however, is better shown with the Happy and Sad Ball demonstration. Conservation of energy can be brought up, as well as conversion from potential to kinetic energy when lifting and letting the balls go. A good demonstration to follow up with would be the Large and Small Ball Collision demonstration.
Potential energy is energy objects have stored either by virtue of gravity or of their elasticity. Kinetic energy is energy objects have by being in motion. Let's number the balls one through five. When all five are at rest, each has zero potential energy because they cannot move down any further and zero kinetic energy because they aren't moving.
When the first ball is lifted up and out, its kinetic energy remains zero, but its potential energy is greater, because gravity can make it fall. After the ball is released, its potential energy is converted into kinetic energy during its fall because of the work gravity does on it.
When the ball has reached its lowest point, its potential energy is zero, and its kinetic energy is greater. Because energy can't be destroyed, the ball's greatest potential energy is equal to its greatest kinetic energy. When Ball One hits Ball Two, it stops immediately, its kinetic and potential energy back to zero again. But the energy must go somewhere -- into Ball Two. Ball One's energy is transferred into Ball Two as potential energy as it compresses under the force of the impact.
As Ball Two returns to its original shape, it converts its potential energy into kinetic energy again, transferring that energy into Ball Three by compressing it. The ball essentially functions as a spring. This transfer of energy continues on down the line until it reaches Ball Five, the last in the line.
When it returns to its original shape, it doesn't have another ball in line to compress. Instead, its kinetic energy pushes on Ball Four, and so Ball Five swings out. Because of the conservation of energy, Ball Five will have the same amount of kinetic energy as Ball One, and so will swing out with the same speed that Ball One had when it hit. One falling ball imparts enough energy to move one other ball the same distance it fell at the same velocity it fell.
Similarly, two balls impart enough energy to move two balls, and so on. But why doesn't the ball just bounce back the way it came? Why does the motion continue on in only one direction? That's where momentum comes into play.
Momentum is the force of objects in motion; everything that moves has momentum equal to its mass multiplied by its velocity. Like energy , momentum is conserved. It's important to note that momentum is a vector quantity , meaning that the direction of the force is part of its definition; it's not enough to say an object has momentum, you have to say in which direction that momentum is acting. When Ball One hits Ball Two, it's traveling in a specific direction -- let's say east to west.
This means that its momentum is moving west as well. Any change in direction of the motion would be a change in the momentum, which cannot happen without the influence of an outside force. That is why Ball One doesn't simply bounce off Ball Two -- the momentum carries the energy through all the balls in a westward direction.
But wait. The ball comes to a brief but definite stop at the top of its arc; if momentum requires motion, how is it conserved?
It seems like the cradle is breaking an unbreakable law. The reason it's not, though, is that the law of conservation only works in a closed system , which is one that is free from any external force -- and the Newton's cradle is not a closed system. As Ball Five swings out away from the rest of the balls, it also swings up.
As it does so, it's affected by the force of gravity, which works to slow the ball down. A more accurate analogy of a closed system is pool balls : On impact, the first ball stops and the second continues in a straight line, as Newton's cradle balls would if they weren't tethered. In practical terms, a closed system is impossible, because gravity and friction will always be factors.
In this example, gravity is irrelevant, because it's acting perpendicular to the motion of the balls, and so does not affect their speed or direction of motion. The horizontal line of balls at rest functions as a closed system, free from any influence of any force other than gravity. It's here, in the small time between the first ball's impact and the end ball's swinging out, that momentum is conserved.
When the ball reaches its peak, it's back to having only potential energy, and its kinetic energy and momentum are reduced to zero. Gravity then begins pulling the ball downward, starting the cycle again. There are two final things at play here, and the first is the elastic collision. An elastic collision occurs when two objects run into each other, and the combined kinetic energy of the objects is the same before and after the collision.
Imagine for a moment a Newton's cradle with only two balls. If Ball One had 10 joules of energy and it hit Ball Two in an elastic collision, Ball Two would swing away with 10 joules. The balls in a Newton's cradle hit each other in a series of elastic collisions, transferring the energy of Ball One through the line on to Ball Five, losing no energy along the way. At least, that's how it would work in an "ideal" Newton's cradle, which is to say, one in an environment where only energy, momentum and gravity are acting on the balls, all the collisions are perfectly elastic, and the construction of the cradle is perfect.
In that situation, the balls would continue to swing forever.
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