physics class
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In this lecture, bound and unbound orbits are discussed. Professor Lewin begins with a description of escape velocity, or the minimum speed required to escape the gravitational pull. Various sources of energy, energy storage, energy conversion, and the world's energy consumption are discussed. Power, or the rate at which a force does work on an object, is central to the conversation. Professor Lewin concludes with a few words on global ...more
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Professor Shankar introduces the course and answers student questions about the material and the requirements. He gives an overview of Newtonian mechanics and explains its two components: kinematics and dynamics. He then reviews basic concepts in calculus through two key equations: x0 + v0t + ½ at2 and v2 = v02+ 2 a (x-x0), tracing the fate of a particle in one dimension along the x-axis.
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This lecture is an introduction to kinematics which ultimately leads (in Lecture 4) to trajectories in three-dimensions. Professor Lewin begins with a description of one-dimensional motion of a particle. He talks about average velocity, the importance of + and - signs, and our free choice of origin. He moves into a conversation about average speed vs. average velocity, instantaneous velocity (reviewing when velocity is zero, posi...more
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Static equilibrium is covered in this lecture, achieved only when the net external force AND net external torque on an object are both zero. A ladder leaning against the wall is analyzed to determine the minimum angle it can make with the floor without sliding. Professor Lewin continues with the topic by discussing how to locate the center of mass of a rigid body. The center of mass always lines up below the point of suspenson such that t...more
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This lecture is a continuation of an analogue to Newton's law: τ= lα. While previous problems examined situations in which τ is not zero, this time the focus is on extreme cases in which there is no torque at all. If there is no torque, α is zero and the angular velocity is constant. The lecture starts with a simple example of a seesaw and moves on to discuss a collection of objects that are somehow subject to a variety of forces but r...more
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This lecture deals exclusively with frictional forces. Starting with a block at rest on a horizontal surface, Professor Lewin describes the normal force, the maximum frictional force that must be overcome to budge the block, and the coefficient of static friction. He continues to make measurements of the coefficient of static friction, and presents ways to reduce friction using hydroplanes and air tracks. Even a flea can move a very heavy...more
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Concepts covered in this lecture include gases and incompressible liquids, Pascal's Principle, hydrostatic and barometric pressure. Professor Lewins concludes with a discussion of overpressure in our lungs. The lung capacity, our ability to overcome hydrostatic pressure, is measured with a manometer. This is related to how deep snorkeling works, and why scuba-divers use pressurized air tanks. Professor Lewin demonstrates that by blowing on...more
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In the absence of a net external torque on an object, angular momentum is conserved. When an object oscillates about an axis of rotation, there is a variable restoring torque acting on the object. A review is given of equations for angular momentum and torque, and the importance of choosing the point of origin. These equations are exercised using an example of a circular orbit.
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We first consider the alternative "Bertrand" model of imperfect competition between two firms in which the firms set prices rather than setting quantities. Then we consider a richer model in which firms still set prices but in which the goods they produce are not identical. We model the firms as stores that are on either end of a long road or line. Customers live along this line. Then we return to models of strategic politics in which it i...more
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In this lecture, Professor Kagan finishes up his description of the Spartan constitution. He argues that Sparta had a mixed constitution and gained great power due to alliances that the Spartans made with their neighbors. After the discussion of Sparta, Professor Kagan examines Athens and the development of the Athenian constitution. In addition, he shows how different these two poleis were. Finally, Professor Kagan discusses the emergen...more
