Work, Energy and Power in CrossFit Problems, Part 1

Dan Fullerton
29 Dec 201304:13
EducationalLearning
32 Likes 10 Comments

TLDRIn this unique lesson, Dan Fullerton explores the physics behind CrossFit exercises at CrossFit Recourse in Webster, NY. By examining work, energy, and power, the video challenges viewers to analyze various exercises such as thrusters, toes-to-bar, rope climbs, and pull-ups. Participants perform the exercises, and viewers are encouraged to solve physics problems related to them. The video promises to reveal solutions in a follow-up, making it an interactive and educational experience for those interested in both CrossFit and physics.

Takeaways
  • 📚 Dan Fullerton introduces a unique lesson analyzing CrossFit exercises from a physics perspective, focusing on work, energy, and power.
  • 🏋️‍♂️ Exercises from CrossFit gym in Webster, New York are used as case studies for the physics analysis.
  • 🔗 A problem set is available for download at the link aplusphysics.com/l/crossfit to aid in understanding the physics concepts discussed.
  • 🤝 The video encourages interaction by suggesting viewers pause to attempt problems before moving on.
  • 🏋️‍♀️ Tom's thrusters are analyzed, including drawing a free body diagram, calculating force, work, power, and net work over 20 seconds.
  • 🏃‍♂️ Chris' toes-to-bar exercises are examined, focusing on the period and frequency of the exercise.
  • 🧗‍♀️ Heidi's rope climb is dissected to determine the minimum force, work, and energy required, as well as her gravitational potential energy and maximum kinetic energy.
  • 🤸‍♂️ James' butterfly chest-to-bar pull-ups are analyzed in terms of frequency and period of execution.
  • 🏃‍♂️ Aaron's box jumps are calculated for work done, minimum energy expenditure, and minimum velocity needed to reach the top.
  • 🔋 The minimum energy expenditure for Aaron to complete 20 jumps and his average power output are discussed.
  • 🌟 The net work done on Aaron by all forces at the end of the exercise is also a point of analysis.
  • 🙏 Special thanks are given to Chris O'Donnell, CrossFit Recourse, and the athletes for their contribution to the video.
Q & A

  • What is the main focus of the lesson conducted by Dan Fullerton?

    -The main focus of the lesson is to analyze the physics of various exercises done at a CrossFit gym, specifically looking at work, energy, and power.

  • Where is the CrossFit gym located that is featured in the lesson?

    -The CrossFit gym featured in the lesson is located in Webster, New York.

  • What is the recommended method for participants to engage with the lesson?

    -Participants are encouraged to download and print out the problem set that can be found at the provided link, and attempt the problems after seeing each exercise and hearing the related questions.

  • How much work is done by Tom when he performs thrusters with a 45 kg barbell?

    -The work done is calculated by the formula Work = Force x Distance. The force here is the weight of the barbell (45 kg * 9.8 m/s^2), and the distance is the height the barbell is lifted (2.2 m - 0.7 m). So, Work = (45 * 9.8) * (2.2 - 0.7) = 45 * 9.8 * 1.5.

  • What is the power developed by lifting the barbell?

    -Power is calculated by dividing the work done by the time taken. In this case, the work done is the result from the previous answer, and the time taken is 2 seconds. So, Power = Work / Time.

  • What is the minimum force Heidi must apply to the rope to move upward?

    -The minimum force Heidi must apply is equal to her weight, which is the product of her mass (50 kg) and the acceleration due to gravity (9.8 m/s^2). So, Force = 50 * 9.8.

  • What is Heidi's gravitational potential energy at the top of the rope?

    -Gravitational potential energy is calculated using the formula PE = m * g * h, where m is mass, g is the acceleration due to gravity, and h is the height. So, PE = 50 * 9.8 * 5.

  • What is the minimum velocity Aaron must leave the ground with to reach the top of the box?

    -To find the minimum velocity, we use the work-energy principle. The work done on Aaron is equal to the change in his kinetic energy. Since work is also equal to force times distance (his weight times the height of the box), and the force is his weight, we can solve for velocity using the equation for kinetic energy (KE = 0.5 * m * v^2).

  • What is the average power Aaron expends during his 20 jumps?

    -Average power is the total work done divided by the total time taken. The total work done is the work per jump (as calculated in the previous answer) times the number of jumps (20). The total time is 52 seconds. So, Average Power = (Work per Jump * Number of Jumps) / Total Time.

  • What is the net work done on Aaron at the end of the exercise by all forces?

    -The net work done is the algebraic sum of all the work done by each force acting on Aaron during the exercise. In this case, since we are only considering the work done against gravity and the work done by gravity when returning to the ground, the net work is zero as these values cancel each other out.

  • What is the period of each exercise performed by Chris in the toes-to-bar exercise?

    -The period of each exercise is the time taken for one complete cycle of the exercise. As Chris performs 20 toes-to-bar exercises in 28 seconds, the period is 28 seconds divided by 20.

  • How is James executing his butterfly chest-to-bar pull-ups?

    -James is executing his butterfly chest-to-bar pull-ups at a frequency that can be determined by dividing the total time (24 seconds) by the number of pull-ups (21). This gives us the time taken for each pull-up, which is the frequency of the exercise.

Outlines
00:00
🏋️ Physics of CrossFit Exercises

The paragraph introduces a unique lesson led by Dan Fullerton, focusing on analyzing CrossFit exercises from a physics perspective, specifically work, energy, and power. The lesson involves exercises performed at CrossFit Recourse in Webster, New York. It encourages viewers to download and print out the associated problem set from the provided link to actively engage with the problems discussed in the video. The video will cover various exercises, including thrusters, toes-to-bar, upper rope climbs, butterfly chest-to-bar pull-ups, and box jumps, with a detailed analysis of each. The video also mentions that solutions will be provided in a subsequent video.

Mindmap
Keywords
💡Physics
Physics is the natural science that involves the study of matter, its motion, and behavior through space and time, as well as related entities such as energy and force. In the context of the video, physics is used to analyze the exercises performed at the CrossFit gym, specifically focusing on work, energy, and power. This is done by applying physical principles to understand the effort and mechanics behind the movements.
💡Work
In physics, work is defined as the measure of energy transfer that occurs when an object is moved by applying force along a displacement. It is calculated as the product of the force applied to an object and the distance over which the force is applied. In the video, work is calculated for exercises such as lifting a barbell in thrusters and climbing a rope, to quantify the effort exerted by the athletes.
💡Energy
Energy is a fundamental concept in physics that describes the capacity to do work. It exists in different forms, such as kinetic energy (related to motion), potential energy (related to position or condition), and thermal energy (related to temperature). The video explores how energy is expended, transformed, and conserved during various CrossFit exercises, particularly focusing on the energy required to perform the movements and the potential energy gained as a result of the athletes' positions.
💡Power
Power in physics is the rate at which work is done or energy is transferred. It is a measure of how quickly work can be performed or energy can be converted. The video analyzes the power developed during the CrossFit exercises, which helps to understand the intensity and efficiency of the workouts. Power is calculated as work done divided by the time taken to do the work.
💡Force
Force is any interaction that causes an object to change its velocity, direction, shape, or deformation. In the context of the video, force is applied by the athletes to move the barbell, their bodies, or other objects during the CrossFit exercises. Understanding the force applied is crucial for calculating work and energy transfer.
💡Gravitational Potential Energy
Gravitational potential energy is the energy an object possesses due to its position in a gravitational field, typically related to its height above a reference point like the ground. In the video, this concept is used to discuss the energy that Heidi gains as she climbs the rope and reaches a higher elevation.
💡Kinetic Energy
Kinetic energy is the energy of motion. An object in motion has kinetic energy, which depends on its mass and velocity. In the video, kinetic energy is relevant when discussing the energy that Heidi and James have at the highest point of their exercises, and the energy that Aaron must expend to jump onto the box.
💡CrossFit
CrossFit is a fitness regimen and exercise program that incorporates elements from various sports and types of training, emphasizing functional movements and high-intensity workouts. The video focuses on the physics behind several CrossFit exercises, aiming to provide a deeper understanding of the physical demands and the biomechanics involved.
💡Exercise
An exercise, in the context of the video, refers to a specific physical activity performed as part of a workout routine, designed to improve strength, endurance, or other aspects of physical fitness. The video analyzes the physics of several exercises, examining the work, energy, and power associated with each movement.
💡Mechanics
Mechanics is a branch of physics that deals with the motion and forces of objects. In the video, mechanics is applied to understand the movement of the athletes' bodies and the objects they interact with during the CrossFit exercises, such as the barbell and the rope.
💡Efficiency
Efficiency in the context of the video refers to how effectively the athletes use their energy to perform the exercises. It is related to the amount of work done, the energy expended, and the power output during the exercises. A more efficient workout would mean that the athletes are able to achieve their fitness goals with less energy wasted.
Highlights

Dan Fullerton introduces a unique lesson analyzing CrossFit exercises from a physics perspective.

The lesson is filmed at CrossFit Recourse in Webster, New York.

Exercises are analyzed in terms of work, energy, and power.

A problem set is available for download to enhance the learning experience.

Tom performs 10 thrusters with a 45 kg barbell in 20 seconds.

A free body diagram is drawn for the barbell to understand the forces involved.

The force applied to raise the barbell is calculated.

Work done and power developed in lifting the barbell are analyzed.

Net work performed on the bar by all forces during the 20 seconds is calculated.

Chris performs 20 toes-to-bar exercises in 28 seconds.

Heidi climbs a 5-meter rope three times, and the minimum force and work required are calculated.

Heidi's gravitational potential energy and minimum energy expenditure are analyzed.

James performs 21 butterfly chest-to-bar pull-ups in 24 seconds.

Frequency and period of each exercise type are calculated for Chris and James.

Aaron jumps onto a 0.6-meter wood box 20 times, and the work done and energy expenditure are analyzed.

The minimum velocity Aaron must leave the ground to reach the top of the box is calculated.

Average power and net work done on Aaron during his 20 jumps are calculated.

The video concludes with thanks to the CrossFit gym and the athletes involved.

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CrossFit PhysicsWork EnergyPower AnalysisExercise MechanicsWebster NYDan FullertonPhysics ProblemsFitness ScienceStrength TrainingAthlete Performance