Online Lab #3 Projectile motion

PHY111,161 ON-LINE LAB, Projectile Motion Lab #3 NAME: Lana Manzanares Projectile Motion NAU UserID: lbm85 Download and save this document to your computer. Answer the questions directly on this document. When you are done, SAVE the file and return it to your TA via BB Learn. Please contact your TA with any questions or other issues. Introduction When we toss a ball through the air, how might we describe its motion? At first, this seems like a very complicated problem, depending on a myriad of variables. However, if we can neglect drag forces that act on the ball, it simplifies the problem greatly. In such a case, the only force acting on the ball is the force of gravity. For much of this lab, we will be investigating this type of simplified projectile motion. Later we will include things like air resistance. There are other small variables that we will be neglecting as completely in this particular lab, such as the curvature of the Earth. Stated simply, projectile motion is a combination of two effects: uniform (non-accelerated) horizontal motion and accelerated vertical motion. Instructions Throughout the majority of this lab assignment, you will be learning about basic (i.e. no drag forces) projectile motion by firing a canon at a target. Go to the web page https://phet.colorado.edu/en/simulation/projectile-motion . Click on the Projectile Motion icon. This will take you to the following page. The simulations go into far more detail than we need in this lab, so we will be utilizing only the Intro lab simulations in our tasks. 1

PHY111,161 ON-LINE LAB, Projectile Motion Task #1 Click on the Intro icon for the following simulation. Take some time to familiarize yourself with how the controls work and the variables that you can change, including the initial speed of the projectile (lower left), the height of the pedestal the canon rests on, the angle of the cannon, and the object that is shot from the canon. You can also drag the target to different distances from the pedestal, toggle air resistance, velocity and acceleration vectors, as well as fire the cannon in normal or slow modes. There’s a tool used to measure time, range, and height which works by placing the crosshair on the dot you wish to measure, there’s also a tape measure. Finally, if the trajectory of the projectile takes it off the screen, you can zoom the picture in or out by using the zoom tool in the upper left corner. Procedure: Reset the simulation (using the curved arrow in the lower right corner), move the cannon pedestal to the ground, angle the cannon at 25 degrees, and select a cannonball. Fire the cannon. Using the simulation tool, measure the maximum height (indicated by the green dot in the trajectory), range, and time of flight of the cannonball. In the table below, record your data. Repeat this procedure for the firing angles indicated. Firing angle (in degrees) Maximum height (in meters) Range (in meters) Time (in seconds) 25 2.05 8.78 .65 35 3.77 10.78 .88 45 5.73 11.47 1.08 55 7.69 10.78 1.25 65 9.42 8.78 1.39 75 10.7 5.73 1.48 85 11.38 1.99 1.52 2

PHY111,161 ON-LINE LAB, Projectile Motion Explain how this makes sense with what you’ve previously observed regarding the vertical and horizontal components of the velocity vector. The horizontal components were never changed, and the vertical vector was consistent; therefore, the acceleration had to be consistent. Task #3 Click on the Lab icon at the bottom of the page. This opens the following simulation: Take some time to familiarize yourself with how the controls work and the variables that you can change. The difference between this simulation and the one we worked with in Task #1 is that we now have additional variables under our control. These variables include the mass and diameter of the projectile, the acceleration due to gravity (for instance if we were on a different planet), and the altitude (in Flagstaff we are around 7000 ft, which is around 2133 meters). We can also account for air resistance now if we wish. 4

PHY111,161 ON-LINE LAB, Projectile Motion Make a prediction: BEFORE running the simulation answer the following: Under the influence of gravity alone (no air resistance), do you think changing the specific projectile launched but keeping the mass and size the same will affect its range? What will happen if you only change the projectiles mass? What will happen if you only change its size? Explain your thinking. I think changing the projectile will change its range even if you keep the mass and size the same. If you change the mass, it will not have as far of a range because it will be heavier and not as easy to move. Test your prediction: Reset the simulation. Set the cannon to the angle that gave the greatest range from Task #1, set the initial speed to 15 m/s , set the item to cannonball , and change the mass to 1 kg using the slider. Fire the cannon. Using the range tool, record the range in the table below. Clear the trajectory by clicking on the eraser (next to the firing button), increase the mass of the cannonball to the maximum, fire the cannon, and measure the range. Repeat the procedure for three other objects with two different masses each (use masses from each end of the slider). Record data in the table below: Item Mass 1 (in kg) Range 1 (in meters) Mass 2 (in kg) Range 2 (in meters) Cannonball 1.00 11.47 31 11.47 Car 2000 11.47 5000 11.47 Football .01 11.47 5 11.47 Human 70 11.47 200 11.47 Using the same items, repeat the experiment, but instead of changing the mass, change the diameter using the slider. Record your information in the table below, using two different diameters for each item. Record the data in the table below: Item Diameter 1 (in meters) Range 1 (in meters) Diameter 2 (in meters) Range 2 (in meters) Cannonball .1 11.47 1 11.47 Car .5 11.47 3 11.47 Football .01 11.47 1 11.47 Human 11.47 1.5 11.47 Questions 5

PHY111,161 ON-LINE LAB, Projectile Motion Car .5 11.36 3 8.72 Football .01 6.31 1 .21 Human 0.5 10.42 1.5 6.39 Questions 1. When air resistance is considered, does changing an item’s mass make a difference in the range of the item? If so, which masses resulted in a greater change to the range (compare your data in this task to similar data from Task #3). When changing the item’s mass, it will make a difference when air resistance is considered. The mass of the football increased causing the greatest change in range. 2. When air resistance is considered, does changing an item’s diameter make a difference in the range of the item? If so, which masses resulted in a bigger change to the range (compare your data in this task to similar data from Task #3). When air resistance is considered, changing the item’s diameter does make a difference in the range of the time. This biggest change was also the football. 3. Do these results make sense to you? Why or why not? These results make sense to me as air resistance and gravity provide a significant change in the range of time. 4. Lastly, consider the Altitude slider. Select a baseball and have the cannon fire it at 30 m/s. Qualitatively, how does the range compare for a city at low altitude vs a city at high altitude? Which altitude should result in more home runs? When comparing the altitude at 0m and 500m the range only increased by about 1 meter. A lower altitude would result in more home runs when considering the runner’s speed. It is easier to run at a lower altitude, so increasing the altitude would not provide a significant amount of change to make a concrete conclusion. 5. Technically, there are even more physical effects at work here, including the Magnus effect. Watch the brief video at: https://www.youtube.com/watch?v=QtP_bh2lMXc and briefly discuss it below: The video shows an experiment comparing the difference in dropping a baseball straight down versus dropping it with a spin. The spin allowed for more power. 6. Watch this short video about The Magnus Force: https://youtu.be/23f1jvGUWJs Now share a few of your thoughts on what you just learned below: The video shows the effects of air on a projectile. The Magnus Force emphasizes the idea of the force on a spinning object. This has a large effect in the sports world when, for example, a football is being thrown, the player would want the football to have a spiral to allow for more force. 7

PHY111,161 ON-LINE LAB, Projectile Motion 7. Read this very brief article The Physics of Baseball Alan M. Nathan University of Illinois http://baseball.physics.illinois.edu/Denver.html What is something you learned that you may not have known before? I have always thought that baseball was a dumb and boring sport compared to another sport such as hockey. In all honesty, it just seemed like a group of boys throwing a ball around. From these articles, I have taken into appreciation the sport of baseball as the way a person throws a ball is all dependent on gravity and force. A person could not just simply throw a baseball and expect it to do what they want. It was interesting to see how physics comes into play with this sport emphasizing the idea of Magnus force. Save this document and return it to your TA via BB Learn. 8