Lab7GravityandOrbits_SCI1055_RG2024

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Lab 7: Gravity and Orbits Ravynn Green SCI1055 2/29/2024 Film 1: Mass versus Weight Introduction Before Viewing 1. Is it possible for an object to change its weight without changing its mass? Explain why or why not. No, it is not possible for an object to change its weight without changing its mass. Weight is directly proportional to mass and the acceleration due to gravity. However, weight can appear to change without any alteration to the mass of the object, if the gravitational field strength changes. 2. What does it mean for something to orbit around the Earth? What keeps the space station in orbit? What if it somehow just stopped in its orbit? What would happen? When something orbits around the Earth, it means that it is moving around the Earth in a closed path due to the gravitational attraction between the object and the Earth. If the space station were to somehow stop in its orbit, several scenarios could occur such as, space falling directly towards Earth, the space station re-entering Earth’s atmosphere and burning up, and if not completely burned up the space stations remaining debris could impact Earth’s surface or ocean. 3. What if you had a “gravity dial” and could turn the strength of gravity up or down? What would happen to your weight as you did that? What would happen to your mass? If you had a hypothetical "gravity dial" that could adjust the strength of gravity, manipulating the hypothetical gravity dial would affect your weight by changing the gravitational force acting on your body but would have no effect on your mass, as mass remains constant regardless of the strength of gravity. Adjusting the gravity dial to increase the strength of gravity would result in an increase in your weight. Your mass would remain constant regardless of the setting of the gravity dial. Mass is a measure of the amount of matter in an object and is independent of gravity. Page 1 of 12

While Viewing 4. The astronauts do some “tricks” to show that they are really in space. What are those tricks and how do they serve as evidence that the astronauts are on board the space station? The tricks performed by astronauts such as back flips, arm wrestling, sumo wrestling, and floating serve as evidence that they are in space because these activities would be impossible or very difficult to do in regular gravity on Earth. After Viewing 5. When you are on a roller coaster, you will feel lighter at the top of the climb, just before you head down. Is this like the weightlessness that the astronauts experience? If so, how are they similar? Also, if so, does it have the same cause? If not, why not? When you are on a roller coaster and feel lighter at the top of the climb, it is because the force you feel is less than your actual weight due to the acceleration pushing you upwards. This sensation is different from what astronauts’ experience in space. Astronauts feel weightless because they are in freefall around the Earth, where they are falling towards the Earth but moving sideways fast enough to miss it. 6. For a given force, why do objects with less mass accelerate at a higher rate? Does this also apply to objects with lower weight? Why or why not? When the same force is applied to objects with different masses, they will accelerate at different rates because acceleration is inversely proportional to mass according to Newton's second law of motion. This means that objects with less mass will accelerate at a higher rate compared to objects with more mass when the same force is applied. Weight, on the other hand, is the force of gravity acting on an object's mass. So, weight is directly proportional to mass. When considering weight, objects with less mass will have lower weight compared to objects with more mass, but this does not directly affect their acceleration rate when the same force is applied. 7. If you took a bowling ball to the Moon and dropped it onto the Moon’s surface, would it be harder or easier (or the same) to lift the bowling ball? If you held it at arm’s length in front of you with 2 hands, would it be harder or easier (or the same) to swing the bowling ball left, and right? When the same force is applied to objects with different masses, they will accelerate at different rates because acceleration is inversely proportional to mass according to Newton's second law of motion. This means that objects with less mass will accelerate at a higher rate compared to objects with more mass when the same force is applied. Weight, on the other hand, is the force of gravity acting on an object's mass. So, weight is directly proportional to mass. When considering weight, objects with less mass will have lower weight compared to Page 2 of 12

objects with more mass, but this does not directly affect their acceleration rate when the same force is applied. Film 2: Mass versus Weight: Accelerating Mass Before Viewing 1. Imagine 2 sealed plastic bags that are exactly the same, except 1 bag is empty and 1 bag is filled with water. On Earth, 1 would weigh more than the other, right? (Which 1 and why?) Now imagine taking both bags into space, where, for all intents and purposes, neither has any weight—yet the 2 bags are still different, are they not? How would you describe the differences? In this scenario, the plastic bag filled with water would have more mass than the empty bag because the water adds to the total mass of the bag. Even though both bags would feel weightless in space, they would still be different in terms of mass, volume, and contents. The mass refers to the amount of matter in an object, volume is the amount of space it occupies, and contents differentiate the two bags based on what is inside them. 2. Imagine a tee-ball setup in which you swing a bat each time with the same force. If you hit a solid wooden sphere and then a hollow plastic sphere with the same force, will the different spheres react differently? If so, how? When you hit the solid wooden sphere and the hollow plastic sphere with the same force, the solid wooden sphere will accelerate faster than the hollow plastic one. This is because the solid wooden sphere has more mass and less ability to absorb the energy from the impact compared to the hollow plastic sphere. As a result, the solid wooden sphere transfers the force more efficiently, leading to a faster acceleration. While Viewing 3. In this demonstration, what provides the force that accelerates the masses? The force that accelerates the masses in this demonstration is provided by the spring inside a tape measurer. 4. What was the result of the third experiment? How did that result compare to the first 2? In the third experiment, the spring inside a measuring tape was able to accelerate a grown man in space. This means that the force generated by the spring was able to move the man. Although this experiment took longer than the first two, it was still successful in achieving the goal of accelerating the man using the spring. After Viewing 5. Why did the empty bag accelerate more rapidly than the full bag? In this case, both bags experience the same force, but the full bag has more mass. Therefore, the full bag accelerates less than the empty bag because it has more mass to move. Page 3 of 12

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6. Amongst all 3 test masses, why did the astronaut have the lowest rate of acceleration? The astronaut had the lowest rate of acceleration among all 3 test masses because the astronaut had a larger mass compared to the other test masses. This means that the larger the mass of an object, the lower its rate of acceleration will be. 7. Why was it important to test objects of different mass? Testing objects with different mass is important because it allows us to observe how mass affects the behaviour of objects in various situations. By testing objects with different masses, we can analyse how forces interact with mass and how mass influences acceleration and motion. 8. Which bag was moving faster by the time it was finished going 1 meter? How do you know? Film 3: Mass versus Weight: Stretching Mass Before Viewing 1. Can you tell how much something weighs just by looking at it? What are the effects of an object’s weight? When you look at an object, you can often make a rough estimate of whether it is heavy or light based on its size, shape, and how it compares to other objects nearby. However, accurately determining the exact weight of an object just by looking at it is not possible. 2. Now consider the same question inside the space station, where objects have mass but appear to be weightless. Could you tell the difference between objects of different mass even if they had no weight? If so, how? Inside the space station, objects are weightless because they are in a state of free fall around the Earth, experiencing microgravity. In this environment, objects of different masses would not be impacted by gravitational force, so they would all appear weightless and float freely. Therefore, it would be challenging to differentiate between objects of different masses solely based on their weight since weight is dependent on the gravitational force acting on an object. 3. What is inside an “empty” bag? An "empty" bag may appear be null of any contents, but there could still be particles of gas or air present inside. While Viewing 4. Do the flexible rings holding the drink bags appear to respond differently when pulled? If so, how? The flexibility of the rings holding the drink bags does not seem to differ significantly when pulled. However, the one on the left may appear slightly bouncier compared to the one on the right. Page 4 of 12

5. The astronaut says 1 of the bags is “full” and 1 is “empty,” but what does she really mean? When the astronaut says one bag is "full" and one is "empty," she is referring to the water in the bags. So, when she says one bag is "full," it means that bag has water, and when she says one bag is "empty," it means that bag does not have any water in it. 6. Which bag do you think is the 1 filled with liquid? What is your evidence? I think the bag on the right is filled with liquid because when the rubber bands are moved, the bag filled with liquid will have a slower acceleration compared to the bag filled with a solid object. After Viewing 7. What are some techniques you might use to test to see which bag has liquid in it and which does not? Stretching the rubber bands to the same length and observing which one has a faster acceleration can help determine which bag has liquid in it and which one does not. This difference in acceleration can be a useful technique to distinguish between the two bags. 8. Explain how an object can have mass but, at the same time, not have weight. In your own words, explain how that is possible. Weight is the force exerted on an object due to gravity. In space, where there is no gravity or gravitational force acting on an object, the object would be weightless. However, mass is the amount of matter contained within an object, and it remains constant regardless of the presence of gravity. So, an object can have mass but not have weight in a scenario like space where there is no gravity. Part II: Gravity Page 5 of 12

Background: Every object around you is attracted to you. In fact, every object in the universe is attracted to every other object in the universe. Newton postulated (around 1666 CE) and Cavendish confirmed (1798 CE) that all objects with mass are attracted to all other objects. We will investigate this relationship. Go to Gravity Force Lab: Basics and select RUN. Qualitative Observations 1. How does the separation of the masses affect the force between them? The force between two masses is directly proportional to the product of the masses. Therefore, if one or both masses are increased, the force between them will also increase. This means that the larger the mass of the objects, the larger the force between them. 2. What happens to the force between the objects when Mass 1 is doubled? When Mass 1 is doubled, the force between the objects is directly proportional to the product of the masses of the objects. Therefore, if Mass 1 is doubled, the force between the objects will also double. 3. What happens to the force between the objects if you cut Mass 2 in half? When you cut Mass 2 in half, the force between the objects decreases. 4. In any of the situations did the two forces ever differ from each other in magnitude. What models apply? In all situations involving gravity, the two forces acting on the masses are equal in magnitude but opposite in direction. 5. In any of the situations, did the forces ever not point in opposing directions? What models apply? No, the forces in gravity are always opposite. Quantitative: Now let us try to build a mathematical model. 1. What 3 things can we change or vary? The mass of object 1, mass of object 2, force applied to objects. 2. Select an independent and dependent variable and a constant. DV: Acceleration of objects IV: Mass of object A Page 6 of 12

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C. Force applied. 3. Collect 10 data points and graph. Remember that your independent variable—the thing you control—goes on the x-axis. (Be sure to label your axes and choose an appropriate scale.) 4. Select a new independent and dependent variable and constant. DV: Acceleration of objects IV: Mass of object B C: Force Applied 5. Collect 10 data points and graph. 6. Repeat the experiment where you varied one of the masses, changing the other mass. You should now have 3 graphs. Be sure to turn those in with this lab. Questions 1. How did varying the second mass affect your results? 2. What is the relationship between mass and force? The force acting on an object is directly proportional to the mass of the object and its acceleration. 3. What is the relationship between distance and the force of gravity? (This is a little tricky. Try to figure it out from your graph, rather than looking it up right away.) The relationship between distance and the force of gravity is as the distance between two objects increases, the force of gravity between them decreases rapidly. In other words, the force of gravity weakens as the distance between the objects increases. 4. Write out the proportions between Mass 1 ( m1 ), Mass 2 ( m2 ) distance ( r ) to the Force of gravity ( Fg ). In other words, write an equation for gravity using the proportionality symbol (α) instead of an = sign. Fg α (m1 * m2) / r^2 If possible, check with your instructor to make sure your proportionality is correct. Send an email and finish the lab tomorrow. 5. Does your lab data for m1 , m2 , and r give F g if you use the proportionalities above? Also work out your units; do they equal a unit of force? 6. Make a graph of force vs. your proportionality. 7. Determine the gravitational constant ( G ) that will satisfy your units. If you are not clear on how to approach this, contact your instructor. G= 8. Explain how you got G from your graph. Page 7 of 12

9. Write your full formula. Page 8 of 12

Part III: Newton’s Cannon Newton’s Cannon: Orbits Isaac Newton explained that universal gravitation accounted for both the fall of an apple and the orbit of the Moon. At the time, this was hard for people to understand. Newton used a thought experiment to show that the same force could explain free fall and orbital motion. In this activity, you will simulate “Newton’s Cannon.” 1. With the settings shown, click the on ‐ screen “Go” button and record your observation. I observe the projectile started at the top, it went down, and then just stopped near the top, leaving a small trail. It takes 8.8 minutes to complete an orbit. 2. Is there anything surprising about what happened? Explain. I was surprised that when we changed the initial speed low to around 50 or less, the projectile motion is just a straight drop down and the trails is very short. 3. Click the on ‐ screen “Reset” button to stop the simulation and restore the initial position and velocity settings. 4. Change the initial speed to 4000 m/s and click “Go.” How is it different from your previous observation? Describe your observations. It is different from the first observation because the projectile motion moves out to the right and further down on the diagram than in the first observation. This observation also takes 10.5 minutes. 5. Change the initial speed to 6000 m/s and click “Go.” How is it different from your previous observation? Describe your observations. It is like the second observation, however its more curved, slower, and is further down on the diagram. 6. Look at your traces for the previous 2 launches. Based on what you see, can you describe a way to fire the ball that will have a different result? Explain. When the initial speed is lower, the projectile motion has less initial kinetic energy, resulting in a smaller curve and a shorter fall time. When we lower the launch altitude, the projectile motion will have a trail that is lower and shorter. 7. Now fire the ball at 7500 m/s. Describe what happens. It has a full orbit around the diagram. 8. What forces are acting on the cannonball in your first 3 launches? What forces are acting on it in your fourth launch? Gravity and resistance from the air. 9. Based on what you have done so far, answer the following: Page 9 of 12

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A cannonball dropped from a cliff will fall straight down and hit the surface of the Earth. How could the cannonball be made to orbit the Earth instead? Defend your answer. If there is enough velocity, a cannonball dropped from a cliff will fall straight down and hit the surface of the Earth. 10. Now describe, in general, how orbits work. Include an explanation of the forces present. Orbits occur when an object, such as a satellite or planet, moves around another object in a closed path under the influence of gravity. Orbits are maintained by the gravitational force between two objects, which provides the centripetal force required to keep the orbiting object moving in a curved path. The velocity of the orbiting object must be sufficient to balance the gravitational pull, resulting in a stable orbit. 11. Keep this website open, as we will be coming back to it, but now open Newton's Mountain. This is a similar site with fewer choices, but it does let us do 1 interesting thing. Fire your cannon at the maximum speed allowed by the simulation and explain the results. What is the word for a velocity that will give these results? The projectile motion went in an outward direction and past the point of the screen. The word for velocity that will give you these results is escape velocity. 12. It is worth noting that planets do not technically orbit the Sun. In reality, the Sun and planets orbit each other. Gravity, like any other force, obeys Newton’s Third Law. The Sun pulls on the planets and the planets pull on the Sun. Most of the planets in our solar system are so small compared to the Sun that the Sun’s resulting acceleration is unobservable. Jupiter, however, is quite large, and the wobble it produces in the Sun’s motion as it orbits is measurable. Go to If You Think Jupiter Orbits the Sun, You're Mistaken to see what this looks like and to read a more detailed description of what is going on. Describe what you see in the video and why it happens. (Note: Be sure you watch the video that shows Jupiter orbiting the sun. It is very short and continuously repeating. There are some other weird videos that sometimes show up at this site.) They are different because the sun orbits in a small circle, while Jupiter orbits in a bigger circle. 13. Now go back to the original simulation for Newton’s Cannon and let us try 1 more thing. Set all your settings back to the ones described in the table above but set the initial speed to 0 and check the box for “Pass through Earth.” Describe what happens and use your understanding of gravity to explain why it happens. It keeps moving from the top to the bottom. Gravity pulls objects toward the center of the Earth, which makes projectile motion fall in a downward motion. When it gets to the bottom, the gravitational force pulls it back up, and resets again. Page 10 of 12

Conclusion: Explain the difference between mass and weight and also the relationship of weight to mass. Discuss the dependence of gravity on mass and distance. Do not just give equations. Describe what happens to the force when you change things. Then discuss how orbits work. What forces are involved? What causes an orbiting object to remain in orbit rather than falling under the force of gravity? What is the effect of increasing or decreasing the object’s speed? Finally, discuss whether you have met the outcomes listed at the beginning of the lab and describe how this lab helped you do that.  Mass refers to the amount of matter contained within an object. It is a measure of inertia, indicating how difficult it is to change the object's motion. Weight, on the other hand, is the force exerted on an object due to gravity. It is the gravitational force acting on an object's mass. Weight and mass are related through the gravitational force acting on an object. The weight of an object is directly proportional to its mass, in which the greater the mass, the greater the weight when subjected to the same gravitational field. An orbiting object remains in orbit rather than falling under the force of gravity because its velocity is balanced by the gravitational force pulling it towards the centre of the body it is orbiting. The object is in a state of continuous free fall around the larger body. If the speed of an orbiting object increases, it may enter a higher orbit or even escape the gravitational pull altogether if the speed exceeds the escape velocity. if the speed decreases, the object may enter a lower orbit or even crash onto the surface of the body it is orbiting if the speed drops below the necessary threshold to maintain orbit. This lab helped me meet the outcomes because it gave instruction to hands on experiences and simulations to help me understand the concepts such as mass, weight, gravity, and orbital mechanics. Works Cited Urone, P. P., Hinrichs, R., Gozuacik, F., Pattison, D., & Tabor, C. (2020). Physics for high school. XanEdu Publishing Inc. OpenStax. (n.d.). https://openstax.org/details/books/physics Page 11 of 12

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