With Spring Training starting up and opening day about a month away, I wanted to do my application blog post on baseball. I thought about different aspects of the game, and then I connected them to what I have learned this year in AP Physics 1. I hope I knocked it out of the park! Motion An interesting new philosophy in the MLB is about the importance of launch angles for hits. According to this article, written during the first half of the 2017 season, hitters are increasingly looking to hit the ball in the air. Daniel Murphy is a leader in this movement because he advocates for “air balls,” or trying to hit fly balls instead of ground balls. This article calls the sweet spot for hits to come at launch angles between 25 and 35 degrees. We learned that the optimal angle for the greatest horizontal distance for a projectile is 45 degrees because this combines time in the air (determined by vertical velocity) with distance traveled (horizontal velocity). With this physics knowledge, I was confused while reading this article because I would expect the sweet spot to be 45° solely based on projectile motion. However, the initial velocity is another important part of the motion of a baseball, and in order to make solid contact with the baseball, it has to come at an angle lower than 45° because otherwise the bat wouldn’t hit the center of the ball. Forces and Motion Here is a physics problem about both motion and forces that can be related to baseball that I found on this website. Sliding into a base causes there to be a force of friction that slows the runner down. This is an oversimplified force diagram because there is also air resistance to take into account, but it helps us solve a problem to find the acceleration of the runner as he slides into second base. Rotational Inertia Two strikes. You step outside of the box and hear your coach remind you to choke up and put the ball in play. Why is this though? The bat undergoes rotational motion throughout a swing, so we can apply physics concepts to help understand this sport. Rotational inertia is an object’s resistance to a change in its angular velocity. It is determined by the distribution of the mass of the object in relation to the fulcrum, or the axis of rotation. The farther away the mass is from the pivot point, the more difficult it is to change its rotational motion so the greater its rotational inertia. Using a regular grip means that the vast majority of the bat’s mass is far away from the axis of rotation, so the bat has a large rotational inertia. However, if a batter chokes up, now the mass is closer to the axis of rotation (smaller radius). This means a choked-up grip causes less rotational inertia, so the batter doesn’t need to apply as great of a torque to affect the motion of the bat. This can be useful in a two strike situation because it gives the batter more control and time for last minute adjustments in order to avoid striking out. Linear and Angular Momentum This Mythbusters article explains why runners slide into bases instead of running to them, and it relates to both linear and angular momentum. If a player runs into second base, he has to slow down in order to avoid overrunning the base and being tagged out. Therefore, the runner must decrease his velocity, which decreases linear momentum (impulse in the opposite direction) which means that it takes longer for the runner to reach the base. On the other hand, starting the motion of sliding causes some linear momentum to become angular momentum (rotate into a headfirst or feet-first position), so the runner doesn’t lose as much momentum as he would by decreasing his translational velocity. Then the runner relies on the friction with the dirt to slow down and then his hands or feet to stop on the base. Here is an interesting video about the physics of sliding and why it is better to slide headfirst than feet-first. Translational and Rotational Kinetic Energy This article talks about how Statcast can now track the different spin rates for pitches. Based on the image below, the key for good pitchers is to have both high velocity and a high spin rate on pitches. I'm going to solve another problem from this document that discusses both translational and rotational kinetic energy of baseball pitches. There is a short summary of some of the ways physics can be applied to baseball! I'm looking forward to this season and I hope the Nationals do well!
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AuthorMy name is Kathleen Boyce and I am a 12th grader at Flint Hill School who is taking AP Physics I. Archives
April 2019
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