Most second-year university engineering students can easily explain the differences between force, torque and pressure. The reason for their confident answers is that engineering schools typically require a term of study in both static and dynamic forces by a students sophomore year. However, from that point on, further studies in these areas are usually confined to aerospace, civil and mechanical engineering disciplines. Few electronic engineers need or will take advanced force mechanic courses.
But modern advances in material properties and device miniaturization as in micro-electro-mechanical systems (MEMS) and sensors mean that force, torque and pressure are relevant across all of the major disciplines. A quick technical review will help remind everyone of these basic concepts.
Force
Simply put, a force is a push or a pull upon an object. A force can cause an object with mass to change its velocity, i.e., to accelerate. Since a force has both magnitude and direction, it is a vector quantity.
A unit of force in the International Systems (or SI) of units is a newton. One newton is defined as the unit of force which would give to a mass of one kilogram an acceleration of 1 meter per second, per second. In terms of an equation, force equals mass times acceleration (F = ma).
Actually, Newtons Second Law of Motion defines force as the change in momentum over time, not mass through an acceleration. But the momentum equation is reduced to F=ma for basic engineering calculations.
Sometimes the word load is used instead of force. Civil and mechanical engineers tend to make calculations based on the load in which a system (e.g., a bridge) is resisting the force of gravity from both the weight of the bridge as well as the vehicles driving over it.
Newtons Laws have been called the basis for space flight. According to NASA, understanding how space travel is possible requires an understanding of the concept of mass, force, and acceleration as described in Newtons Three Laws of Motion. Consider a space rocket in which the pressure created by the controlled explosion inside the rocket's engines results in a tremendous force known as thrust. The gas from the explosion escapes through the engines nozzles which propels the rocket in the opposite direction (Law #3), thus following F=MA (Law #2) which lifts the rocket into space. Assuming the rocket travels beyond Earths atmosphere, it will continue to move into space even after the propellant gas is gone (Law #1).
Newtons Three Laws of Motion
1.
Every object in a state of uniform motion will remain in that state of motion unless an external force acts on it.
2.
Force equals mass times acceleration [F = ma]
3.
For every action there is an equal and opposite reaction.
Torque
The first university course in static forces is usually followed by a course in dynamic forces in which the idea of rational force or torque is introduced. Torque is the tendency of a force to rotate or twist an object about an axis, fulcrum, or pivot. It is the rotational equivalent of linear force.
Formally, torque (or the moment of force) is the product of the magnitude of the force and the perpendicular distance of the line of action of force from the axis of rotation. The SI unit for torque is the newton metre (Nm).
Image Source: Wikipedia by Yawe (Public Domain)
Deriving the equation for torque is often done from a purely force perspective. But it can also be accomplished by looking at the amount of work required to rotate an object. This was the approach the Richard Feynman used in one of his lectures on rotation in two-dimensions.
We shall get to the theory of torques quantitatively by studying theworkdone in turning an object, for one very nice way of defining a force is to say how much work it does when it acts through a given displacement, explained Feynman.
Feynman was able to show that, just as force times distance is work, torque times angle equals work. This point is highlighted in several avionic and aeronautical examples from NASAs Glenn Research Center where NASA designs and develops technologies for aeronautics and space exploration. Force, torque and pressure concepts continue to exert their influences far beyond the earths atmosphere. Concern the release of a large satellite like the Cygnus Cargo Craft from the International Space Station (ISS). The satellite is connected to a large robotic arm that removes it from the ISS prior to release into space. The robotic arm acts just like a huge moment of force in space subject to forces, torques and pressure acting in space.
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Many of us are familiar with gauge pressure from measuring tire pressures. Gage pressure is the pressure relative to the local atmospheric or ambient pressure. This is in contrast to absolute pressure or the actual value of the pressure at any point. This will make more sense shortly.
Pressure is the amount of force acting per unit area. The SI unit for pressure is the pascal (Pa), equal to one newton per square meter (N/m2). Pressure is also measured in non-SI units such as bar and psi.
In his lecture on the The Kinetic Theory of Gases, Feynman introduced the concept of pressure by thinking about the force needed for a piston plunger to contain a certain volume of gas inside a box. The amount of force needed to keep a plunger or lid of area A would be a measure of the force per unit area of pressure. In other words, pressure is equal to the force that must be applied on a piston, divided by the area of the piston (P = F/A).
Applications for pressure technologies exist both on and off the planet. In space, however, pressure is so low that it may almost be considered as non-existent. Thats why engineers often talk about vacuum rather than pressure in space applications. A vacuum is any pressure less than the local atmospheric pressure. It is defined as the difference between the local atmospheric pressure and the point of a measurement.
While space has a very low pressure, it is not a perfect vacuum. It is an approximation, a place where the gaseous pressure is much, MUCH less than the Earths atmospheric pressure.
The extremely low pressure in the vacuum of space is why humans need space suits to provide a pressurized environment. A space suit provides air pressure to keep the fluids in our body in a liquid state, i.e., to prevent our bodily fluids from boiling due to low pressure (via PV = nRT). Like a tire, a space suit is essentially an inflated balloon that is restricted by some rubberized fabric.
Homework question: Why didnt the wheels on the Space Shuttle bust while in space, i.e., in the presence of a vacuum? Look for the answer in the comments section.
In summary, force, torque, pressure and vacuum are important physical concepts that thanks to advances in material sciences and MEMS devices cross all of the major disciplines. Further, these fundamental concepts continue to have relevance in applications like space systems among many others.
Continue reading here:
Tutorial: What are the differences between force, torque, pressure and vacuum? - DesignNews
- A Real Life Hibernation Chamber is Being Made For Deep Space Travel - Futurism - February 7th, 2017 [February 7th, 2017]
- Humans to be FROZEN IN TIME for space travel as scientists move to COLONISE other planets - Express.co.uk - February 7th, 2017 [February 7th, 2017]
- Space flight changes astronauts' brains, research reveals - Fox News - February 7th, 2017 [February 7th, 2017]
- Space travel changes DNA, study finds - STLtoday.com - February 7th, 2017 [February 7th, 2017]
- Space travel visionaries solve the problem of interstellar slowdown ... - Science Daily - February 7th, 2017 [February 7th, 2017]
- Quantum Entanglement May Be Key To Long Distance Space Travel Ex Lockheed Exec Said It's Already Happening - Collective Evolution - February 7th, 2017 [February 7th, 2017]
- Is This Buzz Aldrin-Inspired Locomotive The Future Of Space Travel? - Forbes - February 7th, 2017 [February 7th, 2017]
- Celestial bodies: The Kelly twins offer a vital sign for space travel ... - Pittsburgh Post-Gazette - February 7th, 2017 [February 7th, 2017]
- Space travel visionaries solve the problem of interstellar slowdown at Alpha Centauri - Phys.Org - February 7th, 2017 [February 7th, 2017]
- Newspaper review: Heartthrob and space travel in Wednesday's papers - BBC News - February 8th, 2017 [February 8th, 2017]
- Another View: NASA's Twins Study offers vital sign for space travel - Press Herald - February 8th, 2017 [February 8th, 2017]
- Piece of tragic shuttle history gets a second chance at space travel - WQAD.com - February 9th, 2017 [February 9th, 2017]
- Meet Shawn Pandya, The Third Indian-Origin Woman To Space-Travel - Huffington Post India - February 9th, 2017 [February 9th, 2017]
- Shawna Pandya clears the air on rumours of space travel - Daily News & Analysis - February 10th, 2017 [February 10th, 2017]
- The Expanse and Frankie Adams: Meet the Kiwi who's conquered space travel - Stuff.co.nz - February 10th, 2017 [February 10th, 2017]
- Did a CSU study find that space travel makes you younger? Not so ... - The Denver Post - February 10th, 2017 [February 10th, 2017]
- Twins study offers valuable data on space travel - Herald-Whig - - Herald-Whig - February 10th, 2017 [February 10th, 2017]
- The Expanse and Frankie Adams: Meet the Kiwi who's conquered space travel - Waikato Times - February 11th, 2017 [February 11th, 2017]
- Kelly twins offer a vital sign for space travel - San Angelo Standard Times - February 11th, 2017 [February 11th, 2017]
- Lacoste delves into the world of space travel at New York Fashion Week as Baptista honours founder's lesser-known ... - Evening Standard - February 11th, 2017 [February 11th, 2017]
- NASA's Irish Twins Study reveals first results of space travel on humans - IrishCentral - February 12th, 2017 [February 12th, 2017]
- Starbound to revamp space travel in future update - PC Gamer - February 12th, 2017 [February 12th, 2017]
- How Does Long-Term Space Travel Affect Humans? - Voice of America - February 13th, 2017 [February 13th, 2017]
- A VR Company is Attempting to Make Holographic Videos for Space Travel - Mobile Magazine - February 15th, 2017 [February 15th, 2017]
- Two-Time Space Traveling Astronaut to Speak at Black History ... - Patriots Point - February 16th, 2017 [February 16th, 2017]
- Make space travel great again: NASA, heeding Trump, may add astronauts to a test flight moon mission - National Post - February 16th, 2017 [February 16th, 2017]
- In recently unearthed essay, Winston Churchill anticipated space travel and extraterrestrial life - The Providence Journal - February 16th, 2017 [February 16th, 2017]
- Twins in space: intergalactic travel could change DNA - The Student - February 17th, 2017 [February 17th, 2017]
- An unearthed essay reveals Winston Churchill anticipated space travel and aliens - Stuff.co.nz - February 17th, 2017 [February 17th, 2017]
- Focus Friday: The necessity of space travel - The Daily Cougar - February 17th, 2017 [February 17th, 2017]
- NASA announces $2m investment on technology advancement for deep space travel - WDSU New Orleans - February 17th, 2017 [February 17th, 2017]
- Focus Friday: The necessity of space travel - The Daily Cougar - The Daily Cougar - February 18th, 2017 [February 18th, 2017]
- Ask Ethan: How Can I Travel Through Space Without Getting Into Trouble? - Forbes - February 18th, 2017 [February 18th, 2017]
- Do You Have The Right Personality For Long-Term Space Travel ... - Seeker - February 18th, 2017 [February 18th, 2017]
- In recently unearthed essay, Winston Churchill anticipated space travel and extraterrestrial life - Washington Post - February 18th, 2017 [February 18th, 2017]
- UK bids to be world leader in Space travel by 2020 - Daily Star - February 20th, 2017 [February 20th, 2017]
- Know before you fly: privatized space travel - Observer Online - February 21st, 2017 [February 21st, 2017]
- You could fly to SPACE from the UK within three years as plans are for space port are unveiled - The Sun - February 21st, 2017 [February 21st, 2017]
- Cosmic cinema: spurring interest in real-life space travel? - Miami Student - February 22nd, 2017 [February 22nd, 2017]
- Commercial space travel could be ready as early as 2020 - New York Post - February 22nd, 2017 [February 22nd, 2017]
- This Finnish startup democratizes space travel and it just raised over 3 million to find the next 'Slumdog ... - Business Insider Nordic - February 23rd, 2017 [February 23rd, 2017]
- Commercial space travel WITHIN THREE YEARS on flights to launch from BRITAIN - Express.co.uk - February 23rd, 2017 [February 23rd, 2017]
- Katherine Johnson led African American efforts in space travel - Farm and Dairy - February 23rd, 2017 [February 23rd, 2017]
- Space travel is measured in light years, but what's a light year anyway? - MyStatesman.com - February 23rd, 2017 [February 23rd, 2017]
- TRAPPIST-1: How Long Would It Take to Fly to 7-Planet System? - Space.com - February 24th, 2017 [February 24th, 2017]
- NASA Looking for Bright Ideas to Help With Space Travel - Tech.Co - February 24th, 2017 [February 24th, 2017]
- The history of space travel encapsulated - Fairfaxtimes.com - February 25th, 2017 [February 25th, 2017]
- SpaceX's reusable rockets make space travel much cheaper - The ... - CMU The Tartan Online - February 27th, 2017 [February 27th, 2017]
- Stars align for space travel at memorable Oscars ceremony - Siliconrepublic.com - February 28th, 2017 [February 28th, 2017]
- FSU researcher to lead US-Russia project on health, space travel - Florida State News - February 28th, 2017 [February 28th, 2017]
- Crowding the cosmos: space travel turns private - The Student - March 1st, 2017 [March 1st, 2017]
- Forget SpaceX: 10 companies that will change space travel in 2017 & 2018 - Geektime - March 2nd, 2017 [March 2nd, 2017]
- Safe space travel: Protecting alien worlds from earthlings - and vice versa - Deutsche Welle - March 2nd, 2017 [March 2nd, 2017]
- Watch: 'Black Holes' A Satirical Comedy About Space Travel From Sundance 2017 - Konbini US - March 3rd, 2017 [March 3rd, 2017]
- Doctor Launches Vision Quest To Help Astronauts' Eyeballs - NPR - March 4th, 2017 [March 4th, 2017]
- Beyond Earth talking about space travel - Alaska Public Radio Network - March 4th, 2017 [March 4th, 2017]
- Would You Book A Flight To The Moon? - The Alternative Daily (blog) - March 6th, 2017 [March 6th, 2017]
- Colorado Likely To Benefit From Privatized Space Travel - CBS Local - March 6th, 2017 [March 6th, 2017]
- NEC develops reliable FPGAs for space travel - Electronics Weekly - Electronics Weekly - March 8th, 2017 [March 8th, 2017]
- 4 Entrepreneurs Changing the Way We Think About Space Travel - Tech.Co - March 9th, 2017 [March 9th, 2017]
- Why Space Travel Can Be Absolutely Disgusting - Live Science - March 9th, 2017 [March 9th, 2017]
- EDITORIAL: Exploring private space travel - Indiana Daily Student - March 11th, 2017 [March 11th, 2017]
- Harvard Scientists Theorize That Fast Radio Bursts Come From Alien Space Travel - Popular Mechanics - March 11th, 2017 [March 11th, 2017]
- Space Exploration: US congress approves $19.5 billion for NASA to get humans to Mars by 2033 - NTA News - March 11th, 2017 [March 11th, 2017]
- MIT Conference To Focus On Space Travel For The Public - CBS Boston / WBZ - March 11th, 2017 [March 11th, 2017]
- Reusing rockets is best way to advance space travel, SpaceX officer tells symposium attendees - Colorado Springs Gazette - April 8th, 2017 [April 8th, 2017]
- How space travel leads to cognitive shifts in awareness | Life and ... - The Guardian - April 8th, 2017 [April 8th, 2017]
- Cheap space travel, electric cars and a whirlwind love life love life... the billionaire genius inventing our future - Mirror.co.uk - April 8th, 2017 [April 8th, 2017]
- Reusable rockets key for space travel industry - Alamogordo Daily News - April 8th, 2017 [April 8th, 2017]
- Is this massive airplane the future of space travel? One billionaire thinks so. - SOFREP (press release) (subscription) - June 6th, 2017 [June 6th, 2017]
- spotlight - NYCAviation - June 6th, 2017 [June 6th, 2017]
- BBC commissions documentary about commercial space travel fronted by Brian Cox - Radio Times - June 6th, 2017 [June 6th, 2017]
- The Physics of Interstellar Travel : Explorations in ... - June 6th, 2017 [June 6th, 2017]
- Mars rover scientist, SpaceX engineer join NASA astronaut corps - Reuters - June 7th, 2017 [June 7th, 2017]
- How SpaceX Launched a Chinese Experiment Into Space, Despite US Ban - Foreign Policy (blog) - June 7th, 2017 [June 7th, 2017]
- 'Blast Camp' gives students lessons on space travel - Fremont News Messenger - June 7th, 2017 [June 7th, 2017]
- IKEA looks to space travel for new micro-living furniture collection - Dezeen - June 7th, 2017 [June 7th, 2017]
- HPE's next frontier: Space travel & memory-driven computing - IT Brief Australia - June 8th, 2017 [June 8th, 2017]
- 20 Out-Of-This-World Companies Working On Space Travel Technologies - Interesting Engineering - June 12th, 2017 [June 12th, 2017]
- Here's how space travel is helping keep you healthy - Eyewitness News - June 12th, 2017 [June 12th, 2017]