I’m teaching a summer physics course. One thing I’m doing differently this year is having students do at-home experiments with friends or family. Part of their reporting back involves having to share the ideas of their friend or family member. Here are a few quotes from students discussing what happened when they dropped a book, a piece of paper, and crumpled up piece of paper. Just for context, we discussed this situation on the very first day of class, but we haven’t resolved any of it, and won’t for at least another week. We haven’t even talked about forces yet.
“My friend basically said that the book would for sure hit the ground before the paper did in both of the instances. She thought that because the book is obviously heavier and either way the paper is lighter whether it is flat or in a ball. I would explain the book and paper hitting the ground by saying that when the paper is in a ball then the air isn’t playing any part on the paper. The book and paper have the same gravitational pull.”
“I asked my roommate also in college at MTSU to watch the experiment and give me her ideas on what she thought would happen. Before dropping the flat sheet of paper versus the book she stated that the book would drop first because it was heavier. For the next stage of balling up the paper she stated that the book would still hit the ground first, also that the paper would be closer because we decreased the surface area. She was shocked that they hit at the same time we even tried the experiment with different books to see if the weight of the book would make a difference. As far as my self I am still amazed by this trick. I feel that my friends theory would still hold true for the book versus the flat sheet of paper. I feel that when the paper is in a ball that it has something to do with it being more aerodynamic but other than that it still puzzles and amazes me.”
“I don’t have any roommates or anyone nearby to run this experiment with, but i know most of my friends would have the same reaction as me with the exception of one friend who is in physics right now too. i have no idea how i would explain them hitting the ground at the same time. i guess because the gravitational pull on an object is constant and has nothing to do with the weight of the object, so all you would have to consider between two falling objects is the air resistance or any other resistances on the way down to the ground, and since the uncrumpled paper is far more susceptible to the air force it gets slowed down until it is crumpled into a ball.”
“I did this to my dad. He thought the book dropped first because the paper had air resistance which made it drag. When I crumbled up the piece of paper, he thought that they would hit the floor at the same time which did indeed happen. He said they hit at the same time because the paper has less air resistance all crumbled up. I think the crumbled paper and the book hit the floor at the same time due to not only less air resistance on the paper, but the gravitational pull on both the objects being the same, 9.8 m/s^2 (free-fall)”
“My sister said the book would hit first because it is heavier. When I asked her what would happen with the crumpled up the paper she changed her mind about her first response. She said that the book would hit first the first time because it has less air resistance. I agreed with her about the air resistance being the reason why the book hit first when the paper is flat”
“My mom thought that the book landed first because it was heavier than the piece of paper. Then I asked her what she thought would happen if I crumbled the paper up and she said the same thing. I then explained to her that the gravitational pull remains constant.”
“They said the book falls first because it is heavier than the paper therefore it falls first. when i crumpled the paper they said the book would still hit the ground first because the book is still heavier than the paper. I would explain why the book and paper hit the ground at the same time by explaining that gravity is the same on the book and the paper but since the paper is crumpled up there is less surface for the air to hit and force it to just float down so it falls straight down.”
“Their prediction was that when the paper was crumpled, it might wall slightly faster than it had before, but not as fast as the book, as the paper “became more directed” and “gained more mass when crumpled” …explaining why the book and paper hit the ground at the same time is really not very simple without an understanding of air as a substance. With the book and paper having the same surface area, the book had more weight (mass attraction to earth) and therefore accelerated longer before it could reach a terminal velocity, or equilibrium of resistance to gravitational force. The paper however achieved terminal velocity quickly as its low mass and as such its gravitational attraction, was offset faster. however when the paper was crumpled it lost surface area reducing the force of air on the paper, so even though the paper had the same mass as before, it takes a longer time to reach terminal velocity and accelerates for the most part with the book. ”
“I showed my friend that the book fell first in the first part and she said that it is because the book weighed more. She said that the same thing would happen even if the paper was crumpled up, the book that weighs more would fall first. After seeing that they both hit at the same time she explained that the paper was more aerodynamic the second time and allowed it to fly through the air at the same time as the book. I believe they hit the ground at the same time because the surface area compared to the weight of the object is a factor of resistance. Now that the large surface area is eliminated on the light piece of paper, it could fall at the same velocity as the book.”
What I’m loving about this is that now I have moms, dads, boyfriends, friends, brothers, sisters, roommates in my classroom. Their ideas reaching in and tugging at the idea space our classroom. Our next at-home experiment is the running key-drop. Stay tuned.