Conceptual Physics Alive: Gravity, Satellite Motion
Paul Hewitt teaches about Gravity and Satellite Motion.
Master teacher Paul Hewitt teaches non-computational Conceptual Physics. Observe Hewitt teach in a classroom with real students, using engaging demonstrations and artwork.
DVD Includes 3 Episodes:
Episode 1: Gravity I: The inverse-square law is explained and then related to the law of universal gravitation. Weight and weightlessness, the discoveries of the planets Neptune and Pluto, and the universality of gravitation are also discussed. Segment length: 43 minutes
Episode 2: Gravity II: The discussion of gravitation continues with the emphasis on ocean, earth, and atmospheric tides. Other topics include tunnels through the earth, black holes, the big bang, and speculations of an oscillating universe. Segment length: 42 minutes
Episode 3: Satellite Motion: The concept of simple projectile motion is extended to include satellite motion- first circular, and then, elliptical. After a discussion of escape speed, the tape concludes with a summary of previously learned concepts in mechanics. Segment length: 40 minutes
Gravity I Includes:
• Hewitt begins with patterns that underlie music and the stars.
• Gravitational equation explained with examples and questions.
• Kepler's laws.
• Demonstration of ellipse construction with string and tacks.
• Inverse-square law analogy with light from a candle.
• Questions to illustrate inverse-square law.
• Apparent weightlessness.
• Hewitt steps of table and drops ball (in slow motion} to demonstrate the effects of weightlessness.
• Apparent weightlessness of astronauts in space shuttle.
• Examples of weight at various planetary locations: Infinitely far. At surface of twice-as-massive planet. At surface if your mass doubles. Atop a ladder so you're twice as far from the earth's center.
• Discovery of planet Neptune.
• Von Jolly's determination of G.
• Mass of planet earth.
• Moon's monthly spin.
• Being wrong and analogy of not falling while learning to roller skate.
• Torque and center of mass-gravity explanation of why only one side of the moon faces earth.
Next Time Question: Which pulls harder on the oceans of the earth, the moon or the sun? [The sun out pulls the moon by about 180 times (even though the moon is most effective in raising ocean tides).]
Gravity 2 Includes:
• Hewitt begins with a discussion of ocean tides.
• Hewitt by chalkboard explanation gives an analogy of pulling on a ball of jello in such a way as to deform the jello (like the moon does to the earth's oceans).
• The earth and moon accelerate toward each other as they orbit about a common center of mass.
• The earth rotates daily beneath bulges produced by the moon's pull.
• Hewitt demonstrates the twice-daily tides with a rotating globe.
• The sun's influence in producing tides.
• Explanation of tide variation due to the various positions of the moon and the sun.
• Affects of alignment of sun, moon, and earth, and the new or full moon.
• Moon phases.
• Tides in the molten parts of the solid earth.
• Tides in the atmosphere of the earth.
• Cosmic ray incidence at the earth's surface.
• Zero gravitational field at the earth's center.
• Geometrical explanation of reduced field inside the earth.
• Gravitational field at the surface of a collapsing star.
• Escape speeds at the surface of collapsing stars.
• The concept of a black hole.
• Hewitt stresses the role of equations in guiding thinking.
• The oscillating theory of the universe is discussed.
• Hewitt considers cosmic time via an imaginary graph, and compares the time when fire was discovered with the present, and speculates on how humans will be in the future.
Satellite Motion Includes:
• Begins with a review of the independence of motion via a demonstration of the ball-shoot apparatus.
• The effect of the earth's curvature on projectile motion.
• Cannonball speed to orbit the earth.
• Cannonball shoot from atop Newton's mountain.
• Satellite launching.
• Constancy of speed in circular orbit.
• Bowling alley analogy to satellite motion.
• Vector components.
• Effect of speed on projectile and satellite motion.
• Effect of earth's rotation on satellite motion.
• Elliptical orbits.
• Kepler's misconceptions of satellite motion.
• Kinetic energy and potential energy of satellite motion.
• Burning of satellites that encounter air drag.
• Space shuttle problems and solutions.
• Internal and external ellipses.
• Escape speed.
• Maximum falling speed and escape speed.
Next-Time Questions: Hewitt reviews mechanics in general with a series of questions about a satellite in elliptical orbit. The questions ask for the positions of maximum force, speed, velocity, kinetic and potential energy, total energy, momentum, acceleration, and angular momentum. Equations guide thinking.