Activity 2: How Much Do You Weigh in Outer Space? (Grades 5-8) Objective: The students will demonstrate the ability to apply the use of decimals, fractions, ratios, and proportions to situations based upon given information about planets in the solar system. NCTM Standards: Understand numbers, ways of representing numbers, relationships among numbers, and number systems; Understand the meaning of operations and how they relate to each other; Use computational tools and strategies fluently and estimate appropriately Note to teachers: For this activity, students will be using a chart to compute their weight on different planets and the sun. Students also need a scale to measure their current weight. If you teach students for whom weight is a sensitive subject, modify the activity so that it focuses on the weight of a car, for example, or some other object. Alternatively, students might complete the assignment at home for extra credit. How Much Do You Weigh In Outer Space? Gravity is a universal, natural force that attracts objects to each other. Originally defined by Isaac Newton and later redefined by Albert Einstein, gravity is basically the natural force of attraction between two objects. Two factors determine the magnitude of the gravitational force between two objects: 1) their masses and 2) the separation distance between them. Gravity is the pull toward the center of an object, for example a planet or a moon. When you weigh yourself, you are measuring the amount of gravitational attraction exerted on you by Earth. The moon has a weaker gravitational attraction than the Earth, so you should weigh less on the moon. Isaac Newton showed that the planets do not fly off into space because the gravitational attraction between the sun and each planet hold them close to each other. This attracting force exists between objects because of their mass. The greater the mass, the greater the attraction of gravity. Since every planet has mass, every planet exerts a gravitational force on nearby objects. For this activity, we say that planets have gravity, but actually what we really mean is that there is a gravitational force of attraction between the planet and a person standing on that planet's surface. Therefore, people have different weights on different planets. Complete the chart below (show all work) and then answer the questions that follow. PLANET Multiply your Earth weight by: Mercury 0.4 Venus 0.9 Earth 1 Moon 0.17 Mars 0.4 Jupiter 2.5 Saturn 1.1 Uranus 0.8 Neptune 1.2 Pluto 0.01 Your "new" weight 1. Identify a planet that has a similar gravitational attraction to that of Earth. 2. List the planets' gravitational attraction from least to greatest. 3. Compare the multiplication factors in the chart. Judging from these factors, which planet probably has the greatest mass? 4. Another student claims that the Moon's gravity is 1/6 of the Earth's gravity. Is this a true statement? Look at the chart and use mathematics to support your answer. 5. If your doctor told your aunt that weighing 165 pounds at 5'4" makes her 20 pounds overweight, on which planet would this be an acceptable weight? Justify your answer. Activity 2: Student Worksheet How Much Do You Weigh? Did you know that when the astronauts walked on the moon thirty years ago, they actually weighed less than they did when they left Earth? It wasn't because of any special diet or exercise, either--it could happen to you in outer space, too! Here's an activity that explains why. To complete this activity, you'll need to know your current weight. Gravity is a universal, natural force that attracts objects to each other. Originally defined by Isaac Newton, and redefined by Albert Einstein, gravity is basically the natural force of attraction between two objects. Two factors determine the magnitude of the gravitational force between two objects: 1) their masses and 2) the separation distance between them. Gravity is the pull toward the center of an object; let’s say, of a planet or a moon. When you weigh yourself, you are measuring the amount of gravitational attraction exerted on you by Earth. The Moon has a weaker gravitational attraction than Earth. So, you should weigh less on the Moon. Isaac Newton showed that the planets do not fly off into space because the gravitational attraction between the sun and each planet holds them close together. This attracting force exists between objects because of their mass. The greater the mass, the greater the attraction of gravity. Since every planet has mass, then every planet exerts a gravitational force on nearby objects. For this activity, we say that planets have gravity, but actually what we really mean is that there is a gravitational force of attraction between the planet and a person standing on that planet’s surface. Therefore, people have different weights on different planets. Complete the chart below (show all work) and then answer the questions that follow. PLANET Multiply your Earth weight by: Mercury 0.4 Venus 0.9 Earth 1 Your “new” weight Moon 0.17 Mars 0.4 Jupiter 2.5 Saturn 1.1 Uranus 0.8 Neptune 1.2 Pluto 0.01 1. Identify a planet that has a similar gravitational attraction as Earth. 2. List the planets’ gravitational attraction from least to greatest. 3. Compare the multiplication factors in the chart. Judging from these factors, which planet do you think has the greatest mass? 4. Another student claims that the moon’s gravity is 1/6 of the Earth’s gravity. Is this a true statement? Look at the chart and use mathematics to support your answer. 5. What if your doctor told your aunt that weighing 165 pounds at 5’4” makes her 20 pounds overweight--to what planet could she travel to be at an acceptable weight? Justify your answer. Activity 2: Answers How Much Do You Weigh? 1. Identify a planet that has a similar gravitational attraction as Earth. Venus or Uranus, because their factors are close to 1. 2. List the planets’ gravitational attraction from least to greatest. Pluto, Moon, Mars and Mercury, Uranus, Venus, Earth, Saturn, Neptune, Jupiter, Sun. 3. Compare the multiplication factors in the chart. Judging from these factors, which planet has the greatest mass? The multiplication factors are compared to Earth’s gravity. The factors less than one are planets where the gravitational attraction is weaker than Earth’s, because mass is less. The planet with the greatest mass is Jupiter. 4. Another student claims that the Moon’s gravity is 1/6 of the Earth’s gravity. Is this a true statement. Look at the chart and use mathematics to support your answer. This is a true statement because of the following: A person weighing 80 pounds would weigh (0.17) (80) = 13.6 pounds on the Moon and 13.6 is 1/6 of 80 because 0.17 is approximately 1/6. 5. What if your doctor told your aunt that weighing 165 pounds at 5’4” makes her 20 pounds overweight. To what planet could she travel to be at an acceptable weight? Justify your answer. The student would have to find a gravitational factor that would suffice for a weight at most 145 pounds. 165x = 145 x = .88 Therefore, the best answer would be Uranus with a 0.8 factor. Note, that choosing Venus would only yield the aunt weighing 148.5 pounds.

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