My goal with this post, as with many of my future posts, is to fill a hole in the Internet. That hole is readily accessible information about the kinetic energy of human-propelled objects.
You see, when I watch sports, I often think about physics. I think about energy and forces and friction and velocity. I’m not the only one that thinks about physics in connection with sports. In fact, physics of sports is getting to be big business these days. With professional sports being a multi-billion dollar industry, any possible advantage in competition is worth money. Sometimes science is utilized to help generate competitive advantages in sports. And on the other hand, teachers of physics all around the world have used sports for years to attempt to entice unsuspecting students into being interested in science. I found a great variety of web pages related to the physics of sports while researching for this post.
At any rate, one day while thinking about physics and sports, I thought of a question: what is the object that can be propelled by a human that has the most kinetic energy? There are various objects in sports that are propelled in various ways (thrown/ hit/ kicked/ rolled). What is the method that produces the most kinetic energy? What is the object that, when propelled, has the most kinetic energy?
After having this question, I performed an Internet search to find the answer. I couldn’t find it. I performed various searches, but was never successful in finding the answer. So I determined I would need to calculate the answer myself.
The math to calculate kinetic energy is not difficult. The equation is simply kinetic energy equals half of the value of the mass multiplied by the velocity squared.
So it becomes a matter of simply finding all the values and plugging them in to solve for kinetic energy. I selected a variety of possible winners for objects in sports and plugged in the numbers. The results are shown in the table below, sorted by most kinetic energy on top to the least kinetic energy on the bottom.
First, I will discuss the results, and then make some disclaimers and notes about the data included. I do not include my sources for all of the numbers because the information is fairly readily verifiable except in a few cases as noted below. The first note I must add for consideration in discussing the results is that the numbers shown in the table are mostly maximum values. For example, the fastest speed for a human sprinting is about 12.3 meters per second, which represents Usain Bolt at his peak speed in an Olympic sprint event. This is obviously a lot faster than the average person can run. I applied the same rule to the different objects to find the fastest speeds they can go. So the average person will not achieve similar results to those shown in the table, and maybe not even close. But the maximum results give us a way to compare the different objects.
In looking at the results, the top entry is for a human sprinting, which I don’t consider to be in the category of “human-propelled object”. Thus, that entry is shown only for comparison purposes. Maximum kinetic energy of a human sprinting is approximately eight times the highest kinetic energy of a human-propelled object. This makes sense because when running, a person can continue to add energy to the “object” (their own body) as they pick up speed. The energy doesn’t need to be added all in one short burst as with any propelled object.
The rest of the results in the table were initially surprising to me, and perhaps are surprising to you as well. If I had thought about it some more and done some rough numbers in my head first, the results would not have been surprising (but sometimes one must simply calculate first and think later!). Let me explain. In the kinetic energy equation, the velocity is multiplied by itself while the mass is not. Thus, it would appear that the velocity of an object will be the dominant factor in determining total kinetic energy.
Thus, I figured a golf ball, which I knew must get to some pretty impressive speeds, would yield a high value for kinetic energy. A baseball also gets to relatively high velocities. As you can see, however, these are at the bottom of the table. It is the shot (which is the name of the spherical object that is “put” in a shot put try), with a relatively low velocity, that wins for the propelled object with the most kinetic energy. This is because the shot has a mass that is about 160 times that of the golf ball. While the golf ball does reach speeds five times higher than the shot (resulting in the velocity factor of the kinetic energy being 25 times greater), the shot’s overwhelming mass compared to the golf ball makes a greater difference in yielding a high kinetic energy value of about 750 joules.
The other Olympic throwing sports come right behind the shot put, with the discus around 600 joules and the javelin around 400 joules. A bowling ball, the first real object in the kinetic energy rankings that the average American sporting enthusiast has access to, comes next with about 350 joules. However, the bowling ball spends most of its time limited to rolling along the ground. Along with the preceding objects, the bowling ball is simply propelled into a field of play with no opportunity for further interaction by another player.
Thus, the soccer ball is the first object in the list that is actually “in play” during a sporting competition. That is, a soccer player has the opportunity to absorb the full impact of the almost 300 joules of kinetic energy of the soccer ball. Good thing soccer balls are relatively soft and have a large area of impact!
An arrow, at about 250 joules, and a bullet (typical 22 caliber rifle) at about 100 joules are included in the table for comparison. Obviously, the kinetic energy of a bullet depends significantly upon the type of weapon and bullet (as shown in a table on this blog post, which also includes the kinetic energies of some of the objects included here). However, it is interesting to consider that a soccer ball at high speed can have almost three times the kinetic energy of a typical 22 caliber rifle bullet!
Interestingly, a football and a baseball, when thrown at their respective highest speeds, have approximately the same kinetic energy at about 150 joules. While a football has approximately three times the mass of the baseball, the baseball can be thrown at speeds almost 70% faster than a football, resulting in approximately the same kinetic energy.
Further Discussion and Notes
When I first put the table together, I figured I would need to have separate categories for objects that utilize an external tool to be propelled (such as a golf ball, which is normally propelled by means of a golf club) and those that do not require an external tool, since I figured it would give objects an unfair advantage to have a tool to propel them. However, with the final results, it is clear that the winner, the shot, is an object that does not require an external tool.
One interesting find I had while researching the maximum speed of a football was this article about physics in football with some gross physics errors. The article mentions that the work done by a football quarterback is the force multiplied by the distance, which is approximately correct; however, the distance used in the article is the total distance traveled by the football instead of the distance that should have been used, that traveled by the football during the quarterback’s arm motion. Thus, the work done on the football is calculated at 67,000 joules instead of about 150 joules as it should have been (incidentally, the value used for the force applied is also incorrect), as the work done on the football should approximately equal the kinetic energy of the football as it leaves the quarterback’s hand. This just goes to show you can’t trust everything you read about physics on the Internet.
For baseball, you might wonder if balls can be batted faster than they are pitched. The answer is yes. The maximum speed of a batted ball can get upwards of 120 miles per hour (compared to maximum pitch speed of 100 mph). The forces involved in the collision of baseball to bat can be pretty spectacular, as explained in an article from Popular Mechanics.
It was somewhat difficult to find the maximum speed of a shot put. I ended up just using the world record shot put distance and the fact that a typical shot put launch angle is 40 degrees to solve for shot put speed. There is a related physics homework problem (with fictional data), but the result is that the equation to solve for velocity is:
This yielded a velocity of 14.4 meters per second, which makes sense with a related article that solves for a female Olympic athlete’s shot put speed at 13.5 meters per second.
One object I considered including was an atlatl, but I found it to be not significantly different from an arrow. I thought perhaps hunters before firearms were available would have found a way to get a lot of kinetic energy into an object for survival purposes, but it appears that maximum kinetic energy is not the only consideration in launching a projectile for hunting purposes.
Another object I considered including was a curling stone. However, the speeds of curling stones in competition are so low (two to three meters per second) that the kinetic energy ends up being pretty low as well. I suspect with the right conditions, an athlete could find a way to propel a curling stone at significantly higher rates of speed. Since a stone has a mass of about 18 kilograms (about 40 pounds), the kinetic energy could get pretty high.
I learned a few things about archery. Increasingly sophisticated compound bows have been consistently topping previous arrow speed records in recent years. Also, there is a lot of thought put into the mass of an arrow, and the experts have a lot to say about that. Thus, it is difficult to come up with a good “average” number for arrow mass, but I put what I thought was reasonable based on my research.
Another interesting tidbit I found was that the javelin was redesigned in 1986 to keep throwing distances down. The world record had gotten over 100 meters, which was unsafe for some competitions. I just found it interesting that the record distance was intentionally limited when the usual purpose of Olympic competition is to showcase maximum human abilities.
In calculating the kinetic energy of the various objects, I have neglected rotational kinetic energy. Some objects have a significant amount of spin on them, such as a golf ball with up to 2000 rpm and a baseball with up to 1800 rpm. I won’t go further into that realm in this post, but it may be something to explore in a future post.
So the winner is the shot of the shot put event! So if anyone ever tells you they will give you a dollar for each joule of kinetic energy you can produce by propelling some sports-related object with your own power (I know, this happens to me all the time, too), the shot put is a good choice. You might want to practice your form so you will be ready. And if that circumstance never happens, I hope you enjoyed reading this post and considering the energy of human-propelled objects anyway.
If you are interested, here is the spreadsheet for calculating the kinetic energy of the various objects. You can expand to include your own objects if you want. Let me know what you discover!