Title: How Far Can I Throw a Baseball?
Motion and Forces
1. Newton’s laws predict the motion of most objects. As a basis for understanding this concept:
a. Students know how to solve problems that involve constant speed and average speed.
e. Students know the relationship between the universal law of gravitation and the effect of gravity on an object at the surface of Earth.
i.* Students know how to solve two-dimensional trajectory problems.
j.* Students know how to resolve two-dimensional vectors into their components and calculate the magnitude and direction of a vector from its components.
Materials: Stopwatches, baseballs, meter sticks, field (preferably a football field with lines every 10 yards).
Student prior knowledge: Students must understand how to solve one dimensional kinematics problems, students must also understand how to use vectors to find magnitude and direction.
Explanation: Students will be able to solve for their initial velocity using the three kinematic equations:
Questions & Answers:
If you want to throw the ball as far as you can, at which angle should you release the ball? The ball should be released at about a 45 degree angle, then the ball will go up enough to stay in the air as long a possible, before gravity brings it to the ground, and it will have enough horizontal velocity to travel far in the amount of time that it is in the air.
What are some factors that cause the calculated initial velocity to be different from the actual initial velocity? The calculated numbers are likely different from the actual values because there is air resistance, which our equations do not take into account. There is also human error in the flight time, as a person will not get the exact moment that the ball leaves the person's hands and the moment it hits the ground. It may also be difficult to get an exact distance, as the ball will likely bounce and roll as it hits the ground and it is up to the measurer to figure out exactly where it landed.
Explain how you knew that you could solve for all of the missing values. In both the horizontal and vertical directions, we had three out of the five variables known from our measurements, as we know from kinematics, if we have any three values, we can always solve for the other two. After solving for the missing values, our knowledge of vectors allows us to find the magnitude and direction of the initial velocity.
Applications to Everyday Life: Knowing theses principles can be applied to many sports, anything where a ball is going through the air (soccer, football, baseball, basketball, volleyball, tennis, golf...), it can help students to understand the principles at work for getting the ball from one place to another. These concepts can also be applied to hitting a target (you must aim slightly above your target, because gravity will pull the item down).
Photographs: Include a photograph of you or students performing the experiment/demonstration, and a close-up, easy to interpret photograph of the activity --these can be included later.
Include links to videos posted on the web that relate to your activity.
These can be videos you have made or ones others have made.