2.4 Thinking About Gravity CIT

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Astronomy

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Oct 30, 2023

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2.4 Thinking About Gravity: Core Interactive Text Task: You and a friend are having a discussion about a recent meteor shower. You wonder aloud “why do shooting stars fall, while comets stay in space?” and your friend confidently says “There is no gravity in space, so shooting stars only fall if they pass by and hit the Earth on accident, and then once they get close enough Earth’s gravity causes them to fall”. Something about their statement seems wrong to you, but you can’t quite explain why. When you type the question into Google, the first thing you see is this response: “gravity and inertia act to keep objects in orbit.” You recognize the word inertia, and dig up your notes to remember more about it. Inertia 1. A ball on a string is made to travel in a horizontal circle, as shown below. At point P, the ball is released. Which path will it travel? a. Radially Outwards (straight line away from the center of the circle) b. Tangentially (straight line tangent to the circle) c. Circular (continue moving in a circular path) d. Radially Inwards (straight line towards the center of the circle) Briefly explain your response using the concept of “Inertia.” An object's propensity to resist modifications to its state of motion is known as inertia. If a ball on a string were to move in a horizontal circle, it would have a velocity that is always perpendicular to the circle and a centripetal acceleration that would maintain it moving in a circular motion. Now that you’ve got inertia figured out, you decide to read up some background information on gravity, and find the following short article: “What happens when you jump up into the air? You reach a maximum height and then fall back toward the ground. What happens if you drop a basketball? It falls to the ground because the force of gravity pulls it toward the center of Earth. The force of gravity on Earth pulls everything with mass toward the center of the planet. Since water has mass, it is also pulled downward—just as water runs down the sink drain, water flows toward sea level. This is what causes the water in rivers and streams to flow toward the oceans. The oceans themselves are affected by the gravitational pull of Earth. However, the same force of gravity that pulls objects towards the Earth also pulls objects towards the moon. As the moon orbits Earth, the oceans on Earth closest to the moon experience its gravitational pull. As a result, the water bulges P Radially Outward Radially Inwards Tangential Circular

outward slightly; this phenomenon is known as high tide, and we see it when water rises higher near shores. However, the position of Earth, the moon, and the sun constantly changes. This results in the periodic occurrence of high and low tides.” 2. Most coastlines experience high tide and low tide approximately twice a day, such as this video from the Bay of Fundy near Maine. Explain this pattern using the diagram above. Hint: how long does it take for the Earth to rotate once around its axis? The ocean on the side of the Earth closest to the Moon bulges due to the gravitational pull of the Moon, as depicted in the diagram above, while the water on the other side of the Earth also bulges. Every lunar day, which is roughly 24 hours and 50 minutes long, is thus divided into two high tides and two low tides, with a lag of about 12 hours and 25 minutes separating each. “In sum, the same force that keeps you near the surface of Earth also causes the moon to orbit around Earth, and causes Earth to revolve around the sun. The gravitational force affects the motion of everything in the universe, from microscopic particles to giant galaxies. Without the force of gravity, our solar system would never have even come into existence. Scientists and astronomers believe that the sun and all of the planets in the solar system, including Earth, formed when the force of gravity pulled giant clouds of dust and gas into concentrated clumps. The force of gravity attracted growing clumps of matter toward each other. Eventually the spherical planets we know today took shape. Even today, smaller objects such as asteroids can stray too close to

the planet and have their paths deflected towards Earth due to the gravitational pull--even to the point of impacting the planet directly, such as in the case of meteor impacts.“ 3. Gravity, and all of the four fundamental forces, are spherically symmetric, meaning the direction doesn’t affect the strength of the force--only the distance. How does this explain why planets and stars are spherical in shape? Because gravity is a spherically symmetric force, its strength is only dependent on the separation of objects, not on their orientation. Gravity draws the material towards the center of the forming planet or star, where it is increasingly squeezed. The most stable and effective approach to distribute an object's mass is to give it a spherical shape, which is produced by gravity acting uniformly in all directions. Now that you have read this article, you feel confident you can fully address your friend’s comment about shooting stars. In the space below, evaluate each subclaim from their argument, and revise as needed. Claim Segment Correct or Incorrect? If incorrect, rewrite to make it correct “There is no gravity in space…” Incorrect "There is gravity in space, although its strength may vary depending on the location and mass of objects." “...so shooting stars only fall if they pass by and hit the Earth on accident...” Incorrect "Shooting stars or meteors fall towards Earth due to the gravitational pull of the planet, not on accident." “...and then once they get close enough Earth’s gravity causes them to fall.” Correct "When meteors or asteroids approach the Earth near enough to experience its gravitational attraction, they begin to plummet toward the planet's surface. The object's velocity and trajectory, as well as other elements like the gravitational attraction of other celestial bodies, may also have an impact on how it moves.” Why is there in fact gravity in space, and how does Earth’s gravity affect the motion of asteroids and comets near the planet? Put your revisions together to make a defensible argument to counter your friend’s claim. There is gravity in space, in contrast to the popular misconception that there is none. No matter where two masses are in space, gravity acts between them as a fundamental force of nature. This implies that even celestial objects like comets and asteroids are susceptible to gravity. The motion of asteroids and comets that approach the planet is significantly influenced by the gravity of the Earth in particular. These objects are drawn toward the Earth by the planet's gravitational field as it approaches. If they get close enough, the Earth's gravity may shift their course and send them hurtling into another orbit or into a collision with the planet.

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This is thus because the gravitational force between two objects depends on both their distance and mass. The force of gravity between an object and the Earth increases as it approaches, which may have an impact on the item's velocity. However, an asteroid or comet's response to Earth's gravity relies on a number of variables, including the object's mass, speed, and trajectory. Therefore, the assertion that there is no gravity in space is false. All things in space are subject to the force of gravity, which also influences the velocity of asteroids and comets that approach the Earth.