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1) Fg or Gravitational force or FORCE of gravity (STRENGTH of gravity) depends on 2 factors: a) MASSES of the 2 bodies and b) DISTANCE between the 2 bodies 2) Gravitational force is STRONGER when masses are bigger OR when distance between 2 bodies are CLOSER Gravity: every object in the universe attracts every other object with a force that depends on the MASSES of the 2 objects and the DISTANCES between the 2 objects Inertia: RESISTANCE to change in motion – an object going straight resists change unless a force is applied to it. 2 MAIN factors that effect gravity: 1) mass of objects ; 2) distance between masses Fg = Force of Gravity (or strength of GRAVITY between 2 masses) Fg = (M1x M2) d2 G FORCE of GRAVITY is stronger between 2 bodies when 1) masses are bigger 2) DISTANCES are closer (For example : MOON and EARTH have stronger gravitational attraction to each other than the SUN and the earth because the distance between the MOON and the EARTH is smaller than distance between the SUN and the Earth --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- What were contributions/observations/laws made by: • Galileo (leave 10 lines) • Tyco Brahe (leave 10 lines) • Johann Kepler: Laws of motion (leave 10 lines) • Isaac Newton: Laws of gravity (leave 10 lines) • Albert Einstein: Theory of Relativity (leave half a page) http://astro.unl.edu/naap/lps/animations/lps.swf Same face toward earth (pink); phases -- where is earth relative to sun always 1/2 lit; Gravity on EARTH Gravity on Earth…… affects how fast falling objects fall (they fall at rate of 32 ft/second2 or 9.8 m/second2 http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/physicallaws.htm GRAVITY of Earth affects your weight WEIGHT is pull or force of gravity on your mass weight = Fg = your mass x g g is a CONSTANT gravitational acceleration or gravitational constant on earth: g= 9.8 m/second2) or 32.2 feet/second 2 g has different values on other planets g on GRAVITY combined with INERTIA helps keep 1) the moon revolving around the Earth… 2) Earth revolving around SUN… and 3) all the planets revolving around the SUN….. Without gravity, the planets would all fly off in a straight line into space…… Force GRAVITY and force of INERTIA – MOON held in orbit by Earth’s GRAVITY INERTIA causes moon to move straight; GRAVITY pulls it in toward EARTH In FIGURE of EARTH and MOON Inertia (RED arrow) Moon is moving in a straight line. FORCE of INERTIA resists change of straight line movement. GRAVITY (GREEN arrow) – is FORCE of GRAVITY (attraction) between EARTH and MOON FORCE of GRAVITY applied to object moving in straight line overcomes FORCE of INERTIA and effectively tugs moon inwardly toward earth from its STRAIGHT path. Moon and Earth revolving around each other and a center of mass (+) http://www.sailingissues.com/navcourse6.html Gravity and inertia cause all planets to revolve around SUN Intertia gravity Gravity between the Earth, the MOON and the SUN causes 1) TIDAL bulges 2) Thicker crust on side of moon facing EARTH 3) Wobble in Earth’s orbit 1) MOON’s gravitational effect on earth is TIDAL bulges (TIDES!!!) 2) EARTH’s gravitational effect on the moon is - Thicker moon crust on FAR side of moon that always faces AWAY from earth (same side of moon faces earth – we have NEVER seen back side of moon except from pictures of a satellite that passed behind the moon) http://astro.unl.edu/naap/lps/animations/lps.swf Same face toward earth (pink); phases -- where is earth relative to sun always 1/2 lit; 3) Slight Wobble in Earth’s path due to pull of moon on earth in FULL and NEW moon positions http://www.valdosta.edu/~cbarnbau/astro_demos/tides/neap_sp.ht ml -http://www.mmscrusaders.com/newscirocks/tides/tideanim.htm 2 main types: SPRING NEAP Tides: 2 high and 2 low every 24 hours Tides rise 50 minutes later each day http://home.hiwaay.net/~krcool/Astro/moon/moontides/ http://highered.mcgraw-hill.com/sites/dl/free/0072482621/59233/5_5.htm lows 2 times per 24 hours Earth moving into TIDAL bulges 2 times per 24hr and TIDAL Moon’s pull on tidal bulge slows Earth’s rotation Earth pulls moon ahead in its orbit Net result is earth wobbles a bit in its orbit as moon orbits around it; Earth’s pole now points to Polaris (north star) but pole is being shifted; in 13,000 years VEGA will be our NEW North star . • • Figure 15.4 Solar System Formation The condensation theory of planet formation (not drawn to scale; Pluto is not shown in part e). SWIRLING cloud of gas and dust collapse ; • (a) The solar nebula after it has contracted and flattened to form a spinning disk (Figure 15.1b). The large blob in the center will become the Sun. Smaller blobs in the outer regions may become jovian planets. • (b) Dust grains act as condensation nuclei, forming clumps of matter that collide, stick together, and grow into moon-sized planetesimals as a result of GRAVITY pulling the matter together. The composition of the grains depends on location within the nebula – • (c) Strong winds from the still-forming Sun will soon expel the nebular gas. By this time, some large planetesimals in the outer solar system have already begun to accrete gas from the nebula. • (d) With the gas ejected, planetesimals continue to collide and grow. The gas giant planets are already formed. • (e) Over the course of a hundred million years or so, planetesimals are accreted or ejected, leaving a few large planets that travel in roughly circular orbits. • • • • Example: gravity attraction between SUN and EARTH m1 = earth mass m2 = sun’s mass = 1000 m1 r = Distance = 1 AU • • • F = g m1 1000m1 r2 FORCE sun-earth _________ • Gravity attraction between EARTH and moon m1 = earth mass m2 = moon’s mass = .25 m1 R = 0.01 AU F = g m1 .25m1 • • • • • • r2 FORCE earth-moon __________ Facts about the moon • • http://www.classzone.com/books/earth_science/terc/content/visualizations/es2501/es2501page01.cfm?c hapter_no=visualization GRAVITY pulls together the pieces • http://astro.unl.edu/naap/lps/animations/lps.swf Same face toward earth (pink); phases -- where is earth relative to sun always 1/2 lit; Gravity: Inertia: every object in the universe attracts every other object with a force that depends on the MASSES of the 2 objects and the DISTANCES between the 2 objects RESISTANCE to change in motion – an object going straight resists change unless a force is applied to it. 2 MAIN factors that effect gravity: 1) mass of objects ; 2) distance between masses Fg = Force of Gravity (or strength of GRAVITY between 2 masses) Fg = G (M1x2M2) d FORCE of GRAVITY is stronger between 2 bodies when 1) masses are bigger 2) DISTANCES are closer (For example : MOON and EARTH have stronger gravitational attraction to each other than the SUN and the earth because the distance between the MOON and the EARTH is smaller than distance between the SUN and the Earth --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- What were contributions/observations/laws made by: SUN at center theory PTOLEMY (time period )– GEOCENTRIC (earth at center of universe) theory COPERNICUS (time period ) - HELIOCENTRIC (sun at center of universe theory) • Tyco Brahe (leave 10 lines) • Galileo (leave 10 lines) • Johann Kepler: Laws of motion (leave 10 lines) • Isaac Newton: Laws of gravity (leave 10 lines) • Albert Einstein: Theory of Relativity (leave half a page) • WHEN MASS of objects INCREASED, what is result? REVISED FORCE of GRAVITY is INCREASED/stronger • • • • • • • • -- means bigger either of the masses, stronger the gravitational force OR as either of the masses is increased, the Force of gravity is increased by the PRODUCT Force of Fg INCREASED by m1 x m2 1Fg m1 x 2m1 = 1 x 2 or 2Fg 2m1 x 2m1 2 x 2 or 4 Fg m1 x 3m1 1 x 3 or 3 Fg 3m1 x 3m1 ____ WHEN MASS of objects INCREASED, what is result? FORCE of GRAVITY is DECREASED /not as strong • • • • • • • -- as distance is increased between masses, the force of gravity is weakened by factor of 1/r2 Force of G DECREASED by R=1r m1----m2 Fg R= 2r m1-----------m2 1/(2r)2 = ¼ of Fg R = 3r m1----------------m3 1/(3r)2 1/9 of Fg R = 4r ________ R =5r ________ WHEN MASS of objects INCREASED, what is result? FORCE of GRAVITY is INCREASED/stronger • • • • • • • • • • 1) means bigger either of the masses, stronger the gravitational force OR as either of the masses is increased, the Force of gravity is increased by the PRODUCT Force of G INCREASED by m1 x m2 1G m1 x 2m1 = 2G 3G 2m1 x 2m1 m1 x 3m1 4G 3m1 x 3m1 ____ 4 m1 x 2m1 ____ 8 m1 x 10m1 ____ WHEN MASS of objects INCREASED, what is result? FORCE of GRAVITY is DECREASED /not as strong • • • • • • • 2) as distance is increased between masses, the force of gravity is weakened by factor of 1/r2 Force of G DECREASED by R=1 m1----m2 1 R= 2 m1-----------m2 1/(2)2 = ¼ R = 3 m1----------------m3 1/(3)2 1/9 R=4 ________ R =5 ________ A B C D INCREASE in MASS A. When 1 mass doubles, force (F) is increased by _______ B. when both masses double, force of gravity is increased by _____________ D. When 1 mass stay the same, but the second mass increase by 3, force of gravity is increased by _____________ INCREASE in DISTANCE A. When distance doubled (radius is 2r), force of gravity (F) is decreased by 1/r2 or 1/22 or 1/4 Our weight – the effect of GRAVITY of mass (EARTH) on another mass (ours) Weight Jumps • The gravitational attraction between the Earth and the moon is strongest on the side of the Earth that happens to be facing the moon, simply because it is closer. This attraction causes the water on this “near side” of Earth to be pulled toward the moon. As gravitational force acts to draw the water closer to the moon, inertia attempts to keep the water in place. But the gravitational force exceeds it and the water is pulled toward the moon, causing a “bulge” of water on the near side toward the moon (Ross, D.A., 1995). On the opposite side of the Earth, or the “far side,” the gravitational attraction of the moon is less because it is farther away. Here, inertia exceeds the gravitational force, and the water tries to keep going in a straight line, moving away from the Earth, also forming a bulge (Ross, D.A., 1995). In this way the combination of gravity and inertia create two bulges of water. One forms where the Earth and moon are closest, and the other forms where they are furthest apart. Over the rest of the globe gravity and inertia are in relative balance. Because water is fluid, the two bulges stay aligned with the moon as the Earth rotates (Ross, D.A., 1995). The sun also plays a major role, affecting the size and position of the two tidal bulges. The interaction of the forces generated by the moon and the sun can be quite complex. As this is an introduction to the subject of tides and water levels we will focus most of our attention on the effects of the stronger celestial influence, the moon. • Inertia, acts to counterbalance gravity. It is the tendency of moving objects to continue moving in a straight line. Together, gravity and inertia are responsible for the creation of two major tidal bulges on the Earth (Ross, D.A., 1995). • • Gravitation, or gravity, is a natural phenomenon by which physical bodies attract with a force proportional to their mass. In everyday life, gravitation is most familiar as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped. Gravitation causes dispersed matter to coalesce (come together), and coalesced matter to remain intact, thus accounting for the existence of the Earth, the Sun, and most of the macroscopic objects in the universe. • Gravitation is responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth; • GRAVITY of the Earth-moon-sun system is responsible for the formation of tides; • GRAVITY is responsible for natural convection, by which fluid flow occurs under the influence of a density gradient and gravity; • GRAVITY is responsible for heating the interiors of forming stars and planets to very high temperatures; • • • • What keeps a planet in orbit around the sun, or the moon around the earth, or other moons around their planets are forces of 1) GRAVITY and 2) inertia. Inertia: resistance to change in motion