@hybeerian I am a philosophy teacher in a school, and did this so my students could reply to your comment (we have been studying Ryle's 'myth of volitions'). You ask "can the energies of yore [sic] internal self exist in another form such as 'ghost' or spirit?" They have answered that question for you: that there is no such thing as an 'internal self' such as states of mind, they are in fact just ways of behaving, and thus physical like the 'carbon moleicles [sic]' that you recognise exist.
I've been watching these videos for close to 4 years now. I love how you can tell the age of his videos by the resolution of the writing. The newer ones are so much more crisp.
The first part is law of Conservation of Energy...... Thermodynamics is about Heat in closed system. ΔU = Q - W could u pls tell more about the heat and adiabatic process.
Adiabatic process is one where heat is neither transfered into or out of the system. Hence Q will be 0. Therefore W will be equal to -U. Now this is equal to -nCv(Ti-Tf). Cv is the specific heat at constant volume (Note - Cv is not only used for isochoric processes as it is thought to be by many. That is a mistake. Cv can be used for adiabatic and isothermal as well) . Now after substituting the expression for Cv. The FINAL eqn for W will be (PiVi-PfVf)/(gamma) - 1. So this just means that if work is done by a gas is positive, volume of the gas will increase and U will be more negative.
Personally, the writing helps; I watch videos where people just talk and it is not nearly as helpful as Khan. Plus, it creates the feeling of being in the classroom, which at the very least, gets me in the thinking mode that my house does not normally provide.
@hybeerian While there may be many different ways to store or to release energy, energy itself is equivalent. The reason that static electricity doesn't kill you is that there isn't enough current (amount of charge passing a given point at any one second) while in an Alternating Current or Direct Current Circuit there can be if there is not enough resistance. This does not mean that the energy itself is any different though. You can also essentially break down all forms of energy into...
Entropy Henry Poincare named the conception of "entropy " as a " surprising abstract " Lev Landau wrote: " A question about the physical basis of the entropy monotonous increasing law remains open " One physicist said : " The entropy is only a shadow of energy“ # History of Entropy 1 - Clausius : dS= dQ / T. 2 - Boltzmann : S= k log W 3 - Planck : h*f = kT logW # The formula of Entropy is : h*f = kT logW Israel Sadovnik Socratus
This is so amazing...I cannot thank you enough KhanAcademy for all the helpful tutorials...It has expanded my knowledge in Chemistry and reduced my worries :) Thank You.
'And then I say no, Mister first law of Thermodynamics' XD 'The way I remember U stands for internal energy? Internal Energy doesn't start with a U!' Hahaha your funny comments in the vids help me to remember the content so much better !
Well i rather waste my time watching him write than to sit at lecture class staring at the ppt slides that confuse me. He's taking his time to help us students understand things that are unclear to us. Your comment was unnecessary and rude...
Seriously, I wish my professor is like Sal. My professor is seriously terrible at explaining everything; I think he does not understand how a student learns.. Thanks Khan Academy.
It can absolutely be applied to digestion. Calories are a unit of measure for heat. By determining the caloric intake, taking into account the efficiency of the human body in processing those calories, you can determine, fairly accurately, how much work the body would need to perform in order to "burn" the calories ingested.
Good question. The law of conservation of energy is precisely why perpetual motion is "impossible". For motion to be perpetual, there would need to be no negative forces acting on the object in motion. As he discusses in the video, friction is one of these negative forces. So, since the law of conservation of energy states that energy cannot be destroyed, it has to go somewhere, right? Well, in the case of friction, the energy is converted from kinetic energy to heat.
I prefer the step by step actually, sticking on a whole lot of information on the screen can make the student confused and then not know how to follow the information.
@hybeerian Thanks for your reply. My argument is essentially that the information in our brains is not energy. It is the result of patterns in our neural network. I will also stress that there is no such thing as one kind of energy or another kind of energy. All energy is equivalent. The energy inside my computer is exactly the same as the energy inside my head. The only difference is in the arrangement of that energy.
Nice presentation! BUT, isn't that air resistance was always present when you threw the ball up and when the ball was falling down? A constant is present in opposite directions (meaning the factor of air resistance is cancelled out), so that the velocity going up should be the same as when going down.
Seriously guys, if you're going to complain about the way he's teaching then i suggest you find someone else, no ones forcing you to watch him specifically, I find his style very effective.
Possible in Earth because kinetic energy can be use to "defy gravity" in order to gain potential energy. But a giant Wheel bigger than a Ferris Wheel is needed to make it happen. All it needs is the propulsion which will be the ball and a propulsion driver.
@hybeerian Sorry for the long reply. A shadow is neither matter or energy, yet they clearly exist. Shadows contain information in that they paint a picture of the object blocking them. However, it would be incorrect to say that the information of the shadow exists as "energy". The previous analogy of the paper can be applied to patterns that your neurons make in your brain. I would say that there is information there, but the energy present in the cells is not it.
technically energy can be created or destroyed, for example, if matter interacts with the correct amount of positron or "anitimatter", it creates a huge amount of energy.
And, when the energy is converted from kinetic to heat, the object decelerates. The only way an object could move perpetually would be if the object was in an "ideal" system void of any forces outside of the object's system.
The First Law of Thermodynamics is an application of the Law of Conservation of Energy. Meaning that the internal energy of the system is equal to the heat/work done to the system. Reference: "Chemistry" by Silberberg, 5th Ed., McGraw Hill
Actually he does! He talks about one of the three principles that compose the First law of thermodynamics. More specifically, this law is called The law of conservation of energy.
@hybeerian Cont... potential and kinetic energy. These are different ways of storing energy, but that does not mean that the energy itself is different. "Fusion energy" as you stated, or the energy released by nuclear fusion is released from the mass defect of a nuclear reaction (a little mass is lost and a lot of energy is gained). "Thermal energy" or heat is the transference of kinetic energy from one substance to another. The energy is being stored in different ways, but it is all the same.
Abel Ubina The WORK OUTPUT is more than double the WORK INPUT. So the theory of entropy is misconception. A 15 ball billiard pool to be strike by white mother ball When I computed the work done in pool (billiard) the white mother ball break the 15ball. F = 30lbs (White Mother Ball); D = 3ft (Distance from the white mother ball to the first ball to strike) SOLVE FOR WORK INPUT W = F X D; W = 30lbs x 3ft = 90Ft.lbs SOLVE FOR WORK OUTPUT First two ball extreme corner of the billiard ball 2 out of 15 ball W = F X D; W = 30lbs x 3ft = 90ft.lbs X 2ball = 180 ft. lbs The remaining ball (13pcs ball) can produce more than 90 ft.lbs The computation shows that the output work done is higher than the input work done Appreciated for your reply Thank you. Abel Urbina
Mechanical energy cannot be transfer to electrical energy without "magnetic field" This was never explained to me when I was in school. For example wind generator use PM magnet and hydro electric turbine because of this reason. PM magnet provides unlimited amount of electron at any given time when use to convert mechanical energy to electrical energy. Therefor energy can be created because this process of conversion can only be sustained by electricity. "Magnet/energy can be created."
Much better than a college lecture though. And it's free, and he does a good job to make sure you understand it, etc....Yeah there really is no reason for you to complain other than being a brat.
If energy cannot be created, then it must have existed forever. But if it did, it would have to go back into the infinite beginning of time, which is not in reality. Time does not begin in a moment of time, but in infinity. What would be before it? No time, but no time doesn't continue, so time would replace no time. Only the abstract concepts, such as love, hate, math, geometry, truth, etc. exist there. If you tried to find their beginning, they would be there no matter how far you go back. Only at infinity would you find their source, but not energy; it is generated in a moment of time. Energy has to come from a created source in real time-space.
@kroflet There is, the ball is trasnferring its kinetic energy into thermal energy when its traveling against gravity as well. He made it seem like the force that accelerated the ball upwards was much greater then when the force of gravity acceled it downwards.
Magnet is a source of energy and it can be created. It is scientifically proven that electrons can be harness from magnet for hundred of years before it runs out of energy.
@hybeerian The 1st law of thermodynamics only applies to energy, and not information. Therefore, the information content of your brain is not guaranteed to survive your death. Also, the energy in your neural impulses is constantly converted to other forms and does not stay in your body until death. This is why your brain constantly needs more energy, and it receives it from ATP. The energy in your brain today, is different than the energy of your brain yesterday.
That's basically what happens at school on white boards anyway. It is actually useful as it gives time for the brain to reflect on the words being said.
Does the First Law of Thermodynamics apply to cold and heat energy or does it extend into types of energy like electricity (or even bio-electric -neurons) for example? If anyone can help me with this curiosity please send me a reply. Thank you.
i have question: A glass cleaned in 45celcius hot water and placed on the table bottom up. The room air at 20 celcius that was trapped in theglass gets heated up to 40 celcius and some of it leaks out so the net resulting pressure inside is 2 kPa above ambient pressure of 101kPa. Now the glass and the air inside cools down to room temperature. what is the pressure inside the glass?
When the ball is in motion the mass also changes. E=MCsquare Energy increased so to balance it mass shound increase as C which is speed of light in vacuum is constant.
So it was said that atoms don't really have rotational energy but molecules potentially do bc of sigma bonds that are able to rotate. However, atoms have atomic spin. Doesn't that translate into rotational energy? Was this an accidental omission or do atoms also have rotational energy? Much gratitude for your videos!
All who state that the universe came into existence from nothing violate the first law of thermodynamics. Matter has not always existed. It was created.
If you had a tool to help you learn and be successful/pass thermo, what would you need in the tool? What issues/challenges did you experience taking thermo? What do you do when you are "stuck" and how do you get unstuck? If you have disabilities, what are accessibility needs to utilize an online tool? Why is thermo a difficult coarse?
Then go watch one of his more advanced videos then. His lessons are designed for those with no background in the field, thus why he explains the fundamentals slowly. You know, that almost makes sense.
Debatable; One possible resolution is that the energy which now makes up our universe always existed. Alternatively, all the energy in the universe has a negative counter part, so that the net energy is 0. I wouldn't count Mr. first law out just yet!
@karozans yup, string theory is a perfectly reasonable theory that is fully able to explain everything. however it prove to be near impossible to prove. so in the current state of technological advances, conservation of mass and energy is still the dominant theory
@ChirtyPoundsOfBoost Thanks! So the air resistance when the ball is being thrown upwards is much smaller than AR when the ball is moving back to the ground? Therefore, it's not "worth" mentioning the upward resistance?
First law of thermodynamics- Never talk about thermodynamics.
👎🏻
is that a ******* ****** reference ?
@@iAnesxxdefinitely 😂
He really understands the value of intuition when teaching hard to grasp concepts, that's why his material is the best. Cheers.
U for internal energy. The way I remember that is internal does not start with a U.
+eragon2121 I read this before I got to it in the video and was so confused
eragon2121 sodium starts with S but its NA in chemistry
Black Swan its natrium in most languages
Neither does initial velocity start with u.
You are wrong, it's unternal energy.
That Is like the first law of everything.
Raj Harsh คััา
worse
Dude you are some of the best professors out there you make mine look like a disappointment.
@ aniswar lax 🤣🤣
@hybeerian I am a philosophy teacher in a school, and did this so my students could reply to your comment (we have been studying Ryle's 'myth of volitions'). You ask "can the energies of yore [sic] internal self exist in another form such as 'ghost' or spirit?" They have answered that question for you: that there is no such thing as an 'internal self' such as states of mind, they are in fact just ways of behaving, and thus physical like the 'carbon moleicles [sic]' that you recognise exist.
I cannot thank you more! You are simply amazing. A gift to the people who are eager to learn!
I've been watching these videos for close to 4 years now. I love how you can tell the age of his videos by the resolution of the writing. The newer ones are so much more crisp.
And your comment was made 6 years ago..
@@wings4994 thanks for the flash back
@just some guy tired of life my friend I’ve had this TH-cam account since 2007
When you realize, that you spent hours surfing the internet looking for this stuff explained, and they were here ALL THE TIME. Great courses.
My favorite part: "U for internal energy... The way I remember this is because 'Internal' does not begin with 'U' " lol
Khan, you're the best! Literally life saver for my exam in 3 days.
My exam in 2 days lol
My exam is tomorrow lol
My exam passed LoL.
My exam is today
My exam is an hour away
8:00 internal energy
Be grateful that someone is willing to spend their time teaching you
The first part is law of Conservation of Energy......
Thermodynamics is about Heat in closed system. ΔU = Q - W
could u pls tell more about the heat and adiabatic process.
Adiabatic process is one where heat is neither transfered into or out of the system. Hence Q will be 0. Therefore W will be equal to -U. Now this is equal to -nCv(Ti-Tf). Cv is the specific heat at constant volume (Note - Cv is not only used for isochoric processes as it is thought to be by many. That is a mistake. Cv can be used for adiabatic and isothermal as well) . Now after substituting the expression for Cv. The FINAL eqn for W will be (PiVi-PfVf)/(gamma) - 1.
So this just means that if work is done by a gas is positive, volume of the gas will increase and U will be more negative.
Khan post too many videos. Coolest people ever
Personally, the writing helps; I watch videos where people just talk and it is not nearly as helpful as Khan.
Plus, it creates the feeling of being in the classroom, which at the very least, gets me in the thinking mode that my house does not normally provide.
@hybeerian
While there may be many different ways to store or to release energy, energy itself is equivalent. The reason that static electricity doesn't kill you is that there isn't enough current (amount of charge passing a given point at any one second) while in an Alternating Current or Direct Current Circuit there can be if there is not enough resistance. This does not mean that the energy itself is any different though. You can also essentially break down all forms of energy into...
Love you khan academy
Entropy
Henry Poincare named the conception of "entropy "
as a " surprising abstract "
Lev Landau wrote:
" A question about the physical basis of the
entropy monotonous increasing law remains open "
One physicist said :
" The entropy is only a shadow of energy“
#
History of Entropy
1 - Clausius : dS= dQ / T.
2 - Boltzmann : S= k log W
3 - Planck : h*f = kT logW
#
The formula of Entropy is : h*f = kT logW
Israel Sadovnik Socratus
This is so amazing...I cannot thank you enough KhanAcademy for all the helpful tutorials...It has expanded my knowledge in Chemistry and reduced my worries :) Thank You.
'And then I say no, Mister first law of Thermodynamics' XD
'The way I remember U stands for internal energy? Internal Energy doesn't start with a U!'
Hahaha your funny comments in the vids help me to remember the content so much better !
I think Sal's favorite word is "intuitive" ;)
Well i rather waste my time watching him write than to sit at lecture class staring at the ppt slides that confuse me. He's taking his time to help us students understand things that are unclear to us. Your comment was unnecessary and rude...
Khan this is very useful ......
Seriously, I wish my professor is like Sal. My professor is seriously terrible at explaining everything; I think he does not understand how a student learns.. Thanks Khan Academy.
Thanks .But I have a question.Are we serving as a system or as a surrounding ?
It can absolutely be applied to digestion. Calories are a unit of measure for heat. By determining the caloric intake, taking into account the efficiency of the human body in processing those calories, you can determine, fairly accurately, how much work the body would need to perform in order to "burn" the calories ingested.
Good question. The law of conservation of energy is precisely why perpetual motion is "impossible". For motion to be perpetual, there would need to be no negative forces acting on the object in motion. As he discusses in the video, friction is one of these negative forces. So, since the law of conservation of energy states that energy cannot be destroyed, it has to go somewhere, right? Well, in the case of friction, the energy is converted from kinetic energy to heat.
Awesome, good practice for remembering for a ME graduated some years ago!!!
I prefer the step by step actually, sticking on a whole lot of information on the screen can make the student confused and then not know how to follow the information.
does this guy just know everything. no matter what class im struggling with, he's got something up his sleeve lol
The third law of thermodynamics is that if some yells "stop" or goes limp, taps out, the fight is over
@hybeerian
Thanks for your reply. My argument is essentially that the information in our brains is not energy. It is the result of patterns in our neural network. I will also stress that there is no such thing as one kind of energy or another kind of energy. All energy is equivalent. The energy inside my computer is exactly the same as the energy inside my head. The only difference is in the arrangement of that energy.
Nice presentation! BUT, isn't that air resistance was always present when you threw the ball up and when the ball was falling down? A constant is present in opposite directions (meaning the factor of air resistance is cancelled out), so that the velocity going up should be the same as when going down.
I understand you better than my lecturer.. thanks so much khan academy
You are really AWESOME! thanks for being such a great help!!
Seriously guys, if you're going to complain about the way he's teaching then i suggest you find someone else, no ones forcing you to watch him specifically, I find his style very effective.
Possible in Earth because kinetic energy can be use to "defy gravity" in order to gain potential energy. But a giant Wheel bigger than a Ferris Wheel is needed to make it happen. All it needs is the propulsion which will be the ball and a propulsion driver.
You're better than my physics lecturers ANY day
@hybeerian
Sorry for the long reply. A shadow is neither matter or energy, yet they clearly exist. Shadows contain information in that they paint a picture of the object blocking them. However, it would be incorrect to say that the information of the shadow exists as "energy". The previous analogy of the paper can be applied to patterns that your neurons make in your brain. I would say that there is information there, but the energy present in the cells is not it.
wow physics on chemistry! this helps since Im takng physics 1 with chem 2.
wow this was so easy to understand. If only one of my teachers came close to this.
This is Amazing
Love you sal Khan! You are the best teacher I ever had!
very very good guide,
your not boring at all
technically energy can be created or destroyed, for example, if matter interacts with the correct amount of positron or "anitimatter", it creates a huge amount of energy.
Yea. You can watch the videos at 2x the speed like I do! :D It saves so much time when I am watching lectures or learning things on youtube!
7:32 KE was transferred to air particles (rub) = heat
11:49, 12:44 internal energy (U) - "all the energy that is in a system"
And, when the energy is converted from kinetic to heat, the object decelerates. The only way an object could move perpetually would be if the object was in an "ideal" system void of any forces outside of the object's system.
The First Law of Thermodynamics is an application of the Law of Conservation of Energy. Meaning that the internal energy of the system is equal to the heat/work done to the system.
Reference: "Chemistry" by Silberberg, 5th Ed., McGraw Hill
Khan Academy helped me so much in my development
very few teachers uses this concrete method,,, talented
Actually he does! He talks about one of the three principles that compose the First law of thermodynamics. More specifically, this law is called The law of conservation of energy.
@hybeerian
Cont... potential and kinetic energy. These are different ways of storing energy, but that does not mean that the energy itself is different. "Fusion energy" as you stated, or the energy released by nuclear fusion is released from the mass defect of a nuclear reaction (a little mass is lost and a lot of energy is gained). "Thermal energy" or heat is the transference of kinetic energy from one substance to another. The energy is being stored in different ways, but it is all the same.
He stated that it happens on the way up slightly. You had to listen carefully to hear it.
It’s always U = Q + W . The sign conventions of W differs depends whether ur class is chemistry, physics, or engineering.
this is the coolest video i have ever seen....I love Khan Academy
Abel Ubina
The WORK OUTPUT is more than double the WORK INPUT. So the theory of entropy is misconception.
A 15 ball billiard pool to be strike by white mother ball
When I computed the work done in pool (billiard) the white mother ball break the 15ball.
F = 30lbs (White Mother Ball); D = 3ft (Distance from the white mother ball to the first ball to strike)
SOLVE FOR WORK INPUT
W = F X D; W = 30lbs x 3ft = 90Ft.lbs
SOLVE FOR WORK OUTPUT
First two ball extreme corner of the billiard ball 2 out of 15 ball
W = F X D; W = 30lbs x 3ft = 90ft.lbs X 2ball = 180 ft. lbs
The remaining ball (13pcs ball) can produce more than 90 ft.lbs
The computation shows that the output work done is higher than the input work done
Appreciated for your reply
Thank you.
Abel Urbina
This is making alot of sense thanks you sal for your spend tim to save me from headaches at night😊
I happen to like seeing it written out like a professor with a chalkboard. He could've just not made anything, and it's free.
Mechanical energy cannot be transfer to electrical energy without "magnetic field" This was never explained to me when I was in school. For example wind generator use PM magnet and hydro electric turbine because of this reason. PM magnet provides unlimited amount of electron at any given time when use to convert mechanical energy to electrical energy. Therefor energy can be created because this process of conversion can only be sustained by electricity. "Magnet/energy can be created."
Right after watching this i went outside and threw a rock in the air XD
thanks for this vid! it's really help me in the exams!
Thank you so much! Extremely helpful 👌🏻
I also liked this one..and also apreciate the person who upload these kind of helpful videos... carry on... God Bless you!!
Much better than a college lecture though. And it's free, and he does a good job to make sure you understand it, etc....Yeah there really is no reason for you to complain other than being a brat.
If energy cannot be created, then it must have existed forever. But if it did, it would have to go back into the infinite beginning of time, which is not in reality. Time does not begin in a moment of time, but in infinity. What would be before it? No time, but no time doesn't continue, so time would replace no time. Only the abstract concepts, such as love, hate, math, geometry, truth, etc. exist there. If you tried to find their beginning, they would be there no matter how far you go back. Only at infinity would you find their source, but not energy; it is generated in a moment of time. Energy has to come from a created source in real time-space.
How do you define time?Also does time exist at all?
Time is a measure of change right?
@kroflet There is, the ball is trasnferring its kinetic energy into thermal energy when its traveling against gravity as well. He made it seem like the force that accelerated the ball upwards was much greater then when the force of gravity acceled it downwards.
thank you!
Never argue with an idiot, they'll bring you down to their level and beat you with experience.
Thankyou so much sir you are just amazing.
Magnet is a source of energy and it can be created. It is scientifically proven that electrons can be harness from magnet for hundred of years before it runs out of energy.
@hybeerian
The 1st law of thermodynamics only applies to energy, and not information. Therefore, the information content of your brain is not guaranteed to survive your death. Also, the energy in your neural impulses is constantly converted to other forms and does not stay in your body until death. This is why your brain constantly needs more energy, and it receives it from ATP. The energy in your brain today, is different than the energy of your brain yesterday.
That's basically what happens at school on white boards anyway. It is actually useful as it gives time for the brain to reflect on the words being said.
Does the First Law of Thermodynamics apply to cold and heat energy or does it extend into types of energy like electricity (or even bio-electric -neurons) for example?
If anyone can help me with this curiosity please send me a reply. Thank you.
How many jee aspirants here in 2022 or later
Ahh!! Khan academy always Saves all of the studenta
Thank you for this video,it help me a lot.Greetengs from Serbia
@kroflet No the air resistance is the same, the density of air in this frame of reference is the same.
I think the extra length of the vid is worth watching because you only watch it once, and everything makes sense!
also, I like your voice.
Sal is like the Athleanx of academics
i have question: A glass cleaned in 45celcius hot water and placed on the table bottom up. The room air at 20 celcius that was trapped in theglass gets heated up to 40 celcius and some of it leaks out so the net resulting pressure inside is 2 kPa above ambient pressure of 101kPa. Now the glass and the air inside cools down to room temperature. what is the pressure inside the glass?
took that straight out of my head dude haha
thank you for this interesting video
In what order should i watch all of the thermodynamics content so i can understand the full concept
Thank you khan, you are the man!
When the ball is in motion the mass also changes.
E=MCsquare
Energy increased so to balance it mass shound increase as C which is speed of light in vacuum is constant.
? Energy did not "increase".
U might be onto something, my balls increase in size to compensate for the increased energy while jiggling in a horizontal motion.
So it was said that atoms don't really have rotational energy but molecules potentially do bc of sigma bonds that are able to rotate. However, atoms have atomic spin. Doesn't that translate into rotational energy? Was this an accidental omission or do atoms also have rotational energy? Much gratitude for your videos!
Example of meteorites will be better example than ball. You can see the heat produced by velocity getting transfered to air molecules.
All who state that the universe came into existence from nothing violate the first law of thermodynamics. Matter has not always existed. It was created.
Very well explained!!
If you had a tool to help you learn and be successful/pass thermo, what would you need in the tool? What issues/challenges did you experience taking thermo? What do you do when you are "stuck" and how do you get unstuck? If you have disabilities, what are accessibility needs to utilize an online tool? Why is thermo a difficult coarse?
@ 4:32 he did a perfect circle :)
Then go watch one of his more advanced videos then. His lessons are designed for those with no background in the field, thus why he explains the fundamentals slowly. You know, that almost makes sense.
mind blowing explanation of
U= Q plus or minus W
"no Mr first law of thermodynamics '' this should be a line in a Neil Gaiman book
Debatable;
One possible resolution is that the energy which now makes up our universe always existed.
Alternatively, all the energy in the universe has a negative counter part, so that the net energy is 0.
I wouldn't count Mr. first law out just yet!
@karozans yup, string theory is a perfectly reasonable theory that is fully able to explain everything. however it prove to be near impossible to prove. so in the current state of technological advances, conservation of mass and energy is still the dominant theory
That's why i like his channel!
@ChirtyPoundsOfBoost Thanks! So the air resistance when the ball is being thrown upwards is much smaller than AR when the ball is moving back to the ground? Therefore, it's not "worth" mentioning the upward resistance?