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A brief review. • Force. – A push or a pull. • ‘Nuff said... No longer review.. • Net force. – The overall force on an object after all forces are added together. No longer review.. • Unbalanced forces acting on an object will change the objects motion. No longer review.. • Balanced forces on an object will not change an objects motion. Kind’a stupid example 1 Net Force Net Force Net Force =0 Newton Rocks! Sir Isaac Newton (1642-1727) Sir Isaac Newton “If I have been able to see further, it was only because I stood on the shoulders of giants.” As mathematician, Newton invented integral calculus, and jointly with Leibnitz, differential calculus. He also calculated a formula for finding the velocity of sound in a gas which was later corrected by Laplace. Newton made many contributions to astronomy. He defined the laws of motion and universal gravitation which he used to predict precisely the motions of stars, and the planets around the sun. Using his discoveries in optics Newton constructed the first reflecting telescope. Sir Isaac Newton Before Newton, science seemed a hodgepodge of isolated facts and laws, capable of describing some phenomena, but predicting only a few. Newton provided science with a system of laws that can be applied to a wide range of physical phenomena, and that can be used to make exact predications. Newton published his works in two books, namely "Opticks" and "Principia." Newton’s laws • Newton's First Law of Motion: – Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. – Often termed simply the "Law of Inertia" Wickedly Cool Example 1! • Newton’s first law – An object at rest….. Wickedly Cool Example 2! • Newton’s first law – An object at rest….. • tends to stay that way Deep Thoughts On Physics Deep Thoughts On Physics • Interstellar Mission – The mission objective of the Voyager Interstellar Mission (VIM) is to extend the NASA exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun's sphere of influence, and possibly beyond. Deep Thoughts On Physics • At the start of the VIM, the two Voyager spacecraft had been in flight for over 12 years having been launched in August (Voyager 2) and September (Voyager 1), 1977. Voyager 1 was at a distance of approximately 40 AU (Astronomical Unit - mean distance of Earth from the Sun, 150 million kilometers) from the Sun, and Voyager 2 was at a distance of approximately 31 AU. Deep Thoughts On Physics • Voyager 1 is now at the outer edge of our solar system, in an area called the heliosheath, the zone where the sun's influence wanes. This region is the outer layer of the 'bubble' surrounding the sun, and no one knows how big this bubble actually is. Voyager 1 is literally venturing into the great unknown and is approaching interstellar space. Traveling at a speed of about one million miles per day, Voyager 1 could cross into interstellar space within the next 10 years. Deep Thoughts On Physics • Both Voyagers are headed towards the outer boundary of the solar system in search of the heliopause, the region where the Sun's influence wanes and the beginning of interstellar space can be sensed. The heliopause has never been reached by any spacecraft; the Voyagers may be the first to pass through this region, which is thought to exist somewhere from 8 to 14 billion miles from the Sun. Deep Thoughts On Physics • Sometime in the next 5 years, the two spacecraft should cross an area known as the termination shock. This is where the million-mile-per-hour solar winds slows to about 250,000 miles per hour—the first indication that the wind is nearing the heliopause. The Voyagers should cross the heliopause 10 to 20 years after reaching the termination shock Deep Thoughts On Physics • The Voyagers have enough electrical power and thruster fuel to operate at least until 2020. By that time, Voyager 1 will be 12.4 billion miles (19.9 billion KM) from the Sun and Voyager 2 will be 10.5 billion miles (16.9 billion KM) away. Deep Thoughts On Physics • Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis. In some 296,000 years, Voyager 2 will pass 4.3 light years (25 trillion miles) from Sirius, the brightest star in the sky . The Voyagers are destined—perhaps eternally—to wander the Milky Way Deep thoughts….what if?.. • Both Voyager spacecrafts carry a greeting to any form of life, should that be encountered. The message is carried by a phonograph record - -a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University. Dr. Sagan and his associates assembled 115 images and a variety of natural sounds. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in fifty-five languages. Newton’s laws • The Voyager spacecraft’s endless journey is a great example of Newton’s first law of motion. “An object in motion tends to stay in motion.” Newton’s laws • Newton's Second Law of Motion: – The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma. Acceleration and force are vectors. In this law the direction of the force vector is the same as the direction of the acceleration vector. – Also called the “Law of Constant Acceleration” Newton’s laws • So, if • Then, F = ma….. a = F/m Newton’s laws • Newton's Third Law of Motion: – For every action there is an equal and opposite reaction. – Also called the “Law of Momentum” So…what are the Forces? • Strong force: – – – – The force that holds atomic nuclei together. The strongest of fundamental forces. Has a very short range. Usually attractive, but can sometimes be repulsive. So…what are the Forces? • Electromagnetic force: – Only acts between particles with electrical charge. – Holds atoms and molecules together. – Has a nearly infinite range. – Can be attractive or repulsive. So…what are the Forces? • Weak force: – Is responsible for radioactive decay. – Is much weaker than strong and electromagnetic forces. – Has a very short range. So…what are the Forces? • Gravity: – – – – – The force of attraction between two objects with mass. The weakest of fundamental forces. Has a nearly infinite range. Always attractive, never repulsive. Gravity’s magnitude depends on mass of and distance between objects—the greater the distance, the smaller the force. – Earth’s gravity gives everything weight: • Mass: amount of material in an object. • Weight: force exerted on object’s mass by gravity. So…what are the Forces? • Friction: – The force that slows down or stops the movement of one object in contact with another. – Creates heat—the greater the friction, the greater the heat. – Friction experienced by objects traveling through the air is called air resistance. So…what are the Forces? • Turning force: – Results from two uneven forces independently acting on an object (such as a push and pull). – Causes an object to rotate around a fulcrum. So…what are the Forces? • Centripetal force: – Causes an object traveling in a straight line to follow a curved path. – Usually creates circular motions that move inward toward the center of rotation.