1 / 13

Chapter 4: Newton and Universal Motion

Chapter 4: Newton and Universal Motion. Mechanics. Mechanics = laws of motion Aristotle Rest = Natural State of Motion Heavy objects fall faster Galileo Object continues in motion unless something pushes on it Heavy and light objects fall at same rate. Study of Motion (Mechanics).

cade
Download Presentation

Chapter 4: Newton and Universal Motion

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 4: Newton and Universal Motion

  2. Mechanics • Mechanics = laws of motion • Aristotle • Rest = Natural State of Motion • Heavy objects fall faster • Galileo • Object continues in motion unless something pushes on it • Heavy and light objects fall at same rate

  3. Study of Motion (Mechanics) • Velocity • Change in location Speed (mph) and direction (NE) • Acceleration • Change in velocity (speed and/or direction) • Force • Push or pull (pounds) • Mass • How much stuff (grams, kilograms)

  4. Mass vs Weight mass on Moon = mass on Earth • Mass Produces Gravity • Mass intrinsic to object (never changes) • Gravity proportional to mass • Weight = Force of Gravity • Stand on scale scale pushes back with equal force • Weight proportional to mass • Free-Fall (falling elevator, astronauts) • Acceleration of gravity = weight / mass All objects fall at same rate • Objects appear “weightless” weight on Moon = 1/6 weight on Earth in space, force ofgravity isnot zero

  5. Newton • Laws of Motion • Moving object keeps moving • Same speed • Same direction Objects want to move in straight line • Change in motion (speed or direction) • caused by force acceleration = force / mass • Equal, but opposite, forces between pairs of objects Push on object; it pushes back (just as hard)

  6. Newton • Invents mathematics (calculus) • Used to solve force equations • Circular motion • Direction of motion changes • Requires force • Force changes direction; speed unaltered • Force points toward center of circle

  7. Newton • Gravity • Pulls apple toward earth • makes apple fall Weight = force of gravity • Orbits similar to circles • Newton’s Hypothesis • All objects produce gravity • Sun’s gravity • planets orbit sun • Planet’s gravity • moon orbits planet Gravity Sun

  8. Launching Rockets • Fire Cannon Sideways; keep increasing velocity • Rocket moves sideways; offsets falling • Circular Orbit Speed =17,000 mph • Escape Speed = 25,000 mph

  9. Newton M1 = mass 1st object (sun) M2 = mass 2nd object (planet) R = distance between them G = Newton’s constant (a number) • Law of Gravity Force = G M1M2 / R2 • Double either mass: force increases by 2 • Double distance: force decreases by 4 • Larger (smaller) mass causes larger (smaller) gravitational force. • Larger (smaller) distance causes smaller (larger) gravitational force.

  10. Newton and Planets • Law of Gravity Force = G MsunMplanet / R2 Acceleration = Force / Mplanet = G Msun / R2 • Planet motion: • independent of planet massdepends on: mass of sundistance

  11. Newton and Planets Laws of motion + Gravity • Predicts Kepler’s Laws: • 1st Law (orbits are ellipses) • 2nd Law (equal area in equal time) • conservation of angular momentum • Skater pulls arms in; spins faster • Planet gets closer to sun; goes faster • Extended 3rd Law a3 = M P2 • use to measure mass M (of central body) M in solar masses

  12. Consider a planet orbiting the Sun. If the mass of the planet doubled but the planet stayed at the same orbital distance, then the planet would take • a) more than twice as long to orbit the Sun. • b) exactly twice as long to orbit the Sun. • c) the same amount of time to orbit the Sun. • d) exactly half as long to orbit the Sun. • e) less than half as long to orbit the Sun.

  13. Imagine a new planet in our solar system located 3 AU from the Sun. Which of the following best approximates the orbital period of this planet? • a) 1 year • b) 3 years • c) 5 years • d) 9 years P2=a3, so if a=3, then a3=3x3x3=27; then P2=27, so P~5 (since 5x5=25)

More Related