Astro 7N Exam 1

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Astro 7N Exam 1 The force of gravity by the Sun keeps the planet in orbit around it, but how do the planets affect the sun? - ✔✔They exert an equally strong pull on the sun, causing it move sl ... ightly Newton's First Law - ✔✔An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. ex: if the sun suddenly disappeared, the Earth would continue in the direction that it was traveling in its orbit at that time Newton's Second Law - ✔✔The acceleration of a body due to a force will be in the same direction as the force, with magnitude directly proportional to its mass Force = mass x acceleration A smaller mas will move faster, if the same force is applied to it Newton's Third Law - ✔✔For every action there is an equal and opposite reaction The Sun exerts force on planets, and they orbit it - he planets exert equal force on Sun, but it only moves slightly because of its very large mass relative to the planets Surface Gravity on a Planet - ✔✔the strength of gravity: g = m/r^2 where M is the mass of the planet and R is its radius. Note the radius is squared but the mass is not. More mass = more gravity. - If the mass of a planet were twice that of another, but they had the same radius, the gravity felt on the surface of the more-massive one would be twice as strong. Larger separation = less gravity. - If the radius of a planet were twice that of another, the gravity is 1 / (2) 2 = 1/4 as strong. Putting the effects of mass and radius together, you should be able to figure out the surface gravity of Mars, relative to the Earth. - Mars has 1/10 the mass of the Earth and 1/2 the radius of Earth. So for Mars, g = (1/10) / (1/2) 2 = (1/10) / (1/4) = 4/10 Mars has a surface gravity 4/10 that of Earth. You will need to be able to do this type of estimate for the test, given the numbers for mass and radius. If I apply exactly the same amount of force to a pebble and a boulder, what will happen - ✔✔the pebble will move faster If the Earth were moved to half its current distance from the sun, how would the force of gravity by the sun on the earth change? - ✔✔it would become 4 times weaker Mass - ✔✔As the mass of the planet increases, the jump height does decreases by the same factor As the mass of the planet decreases, the jump height does increases by the same factor According to Newton's Second law of motion, if the net force acting on the object increases while the mass of the object remains constant, what happens to acceleration - ✔✔acceleration increases If the earth were moves to half its current distance from the Sun, how would the force of gravity by the Sun on the Earth change - ✔✔it would become four times weaker What did newton's law of universal gravitation tell us about how gravity works - ✔✔the force of gravity from the sun will be stronger on object with more mass If you were to sit on the ground, there would be a force due to gravity pulling you toward the earth. which of the following is true according to newton's third law - ✔✔you are pushing the earth away from yourself with the same force what would happen to the earth sun's gravity somehow turned off instantaneously - ✔✔it would continue to move in the line in the same direction it was moving when the gravity turned off Newton's Universal Law of Gravitation - ✔✔This law gives the force of gravity between any two objects in the Universe. The force of gravity is proportional to (mass of object 1) × (mass of object 2) divided by the distance between the two objects squared: F M1 x M2 / d 2 Again, more mass = stronger gravity. If the objects were moved 2 times closer (or, to half of their initial distance between), ... F M1 x M2 / (1/2) 2 = M1 x M2 / (1/4) = 4 (M1 x M2) ... so, the gravitational attraction would become 4 times as great. The Seasons, Day & Night - ✔✔Q: What causes day and night? A: Rotation of the Earth on its axis. Q: How does the Sun appear to move in the sky in the course of a day? A: East to West, because of Earth's rotation. The stars and planets move in the same way from our point of view, also, because of Earth's rotation. Q: What happens to the Earth in one year? A: It orbits the Sun, once (also referred to as one complete revolution about the Sun). Q: Why do we have seasons? A: The tilt of the Earth's axis of rotation, with respect to the plane of its orbit around the Sun (and not because of changing distance from Sun). The Earth's tilt is about 23 degrees. Q: How is the Earth's axis tilted when we have summer in the Northern hemisphere? A: With the North pole toward the Sun. Q: What season is it in the Southern hemisphere when it is summer in the Northern hemisphere? A: Winter The Seasons, Day & Night pt2 - ✔✔Winter begins on or about Dec. 21 = in the Northern hemisphere, the nights are longer than days Spring begins on or about March 21 = days and nights have equal length Summer begins on or about June 21 = days longer than nights in the North Fall begins on or about Sept. 21 = days and nights have equal length Seasons would not happen if the Earth's axis were not tilted. The distance between the Earth and the Sun does not change very much over the course of a year, so the temperature does not change much for that reason. Without the tilt of Earth's axis there would be no seasons on Earth. Mars has a similar tilt to its rotation axis as Earth does. if earth rotated on it axis more slowly than it does now; - ✔✔days would be longer if earth had its orbit changed so that all points along its orbit it were always the same distance from the sun (circular orbit), how would this affect the seasons on earth? - ✔✔they would be the same as they are now a new planet orbits its star faster than the earth orbits the sun and it rotates more slowly than he earth rotates. which is true - ✔✔the new planet has a shorter year than earth and a longer day than earth what time of year is it dark all (and night) at the south pole of earth? - ✔✔June When the northern hemisphere is tilted TOWARDS the Sun the average daily temperature is marked as____, suggested that the northern hemisphere is experiencing____ - ✔✔warm;summer And, on the opposite site of the orbit, when the northern hemisphere is tilted the farther away from the sun, the average daily temperature is marked as____, suggesting that the norther hemisphere is experiencing___ - ✔✔cool;winter in the southern hemisphere its___in late june, and__is in late december - ✔✔winter;summer the longest day of the year in the Northern Hemisphere is on or about____ and the shortest is, again, six months later near___, when the earth is at the opposite point in its orbit around the sun - ✔✔June 21 and December 21 These are called summer solstice and winter solstice Two dates are on opposite sides of the earth's orbit near - ✔✔March 21 and September 21 these are called the Vernal Equinox and Autumnal equinox (equal night) Moon Phases and Eclipses - ✔✔Q: What happens to the moon in 1 month? A: It moves once around the Earth. Q: What causes the phases of the Moon? A: The Sun is lighting up different fractions of the part of the Moon we see from Earth. Q: What is the order of the phases of the Moon? A: New - Waxing Crescent - First Quarter - Waxing Gibbous - Full - - Waning Gibbous - Third Quarter - Waning Crescent - New (and repeat...) Q: When is the full moon visible? A: Only at night. It transits (is highest in the sky, or overhead) at midnight; the full moon rises 6 hours earlier (at sunset), and sets 6 hours later (at sunrise). Q: When is the new moon visible? A: The new moon is visible during the day. It transits at noon; it rises 6 hours earlier (at sunrise), and sets 6 hours later (at sunset). Q: How are the Sun, Earth, and Moon positioned when it is new Moon? A: in a straight line: Sun — Moon — Earth Q: How are the Sun, Earth, and Moon positioned when it is full Moon? A: Sun — Earth — Moon Q: What is a solar eclipse? A: The Moon is blocking the Sun's light, or a location on the Earth's surface is passing under the Moon's shadow. Moon Phases and Eclipses pt2 - ✔✔The outer ring of Moons shows the orientation of the Sun- illuminated half its surface; the inner ring of Moons shows how the Moon appears in our sky at those times. The Moon phase directly away from a point on the Earth's surface can be said to be "overhead" at the time of day that corresponds to that [Show More]

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