The introduction of cosine and its values influencing the amount of work really blew my mind for some reason. Being able to quantify things like that really makes me appreciate this crazy universe. These videos are immensely valuable and you are one of the reasons I have chosen to pursue an education in physics
You know you never really use too many examples or if you do they are simple, but honestly that should be the way they initial teach. It really helps me understand where things come from before practicing the actual examples later.
I felt bamboozled knowing that this is the first video that I’ve seen that did not include comprehension in the end. But nonetheless you’re explanation are always superb thank you very much!
thanks very much for the explanations i am having a test tomorrow about work and energy and i feel much clever after i watched this video and i like the way you explain work and energy i cant wait to see more of your videos about KE and PE thanks for the video now even my sister carly can understand
Okay. So here is a very fundamental doubt. We know that work = energy. (It definitely is. Because, work=fd= 1/2mv(v)= energy And energy is the ability to do work..(1) That implies Work=ability to do work (using (1))?😮😮 How can two things which are exactly equal can be different from each other?
im so happy i found a youtuber that can help me with bioligy,chemistry and physicis this means so much to me.. u have no idea how ur helping me with my finals :)
In physics, "work" is when a force applied to an object moves the object in the same direction as the force. If someone pushes against a wall, no work is done on the wall because it does not move. However, depressing a letter on a computer keyboard requires work.
Theeta is a greek letter, just like we use 'x' and 'y' to mark angles. Cos theeta means the effect of that force in the horizontal direction. For example if you hit a football in north-east direction, actually it had travelled in two perpendicular directions, north and east...the force which contributed for the force only to travel to east means Fcos(theeta)..its something like that..... And work energy theorem means that, the more energy u have, the more u can transfer it and do work...just like if u have more money, you can spend to buy more things and vice versa.. in physics, that spending to buy part should be replaced by 'making an object move'(do work)
This makes me think of the old expression every young man is scolded/initiated with into the world of manual labor: *”Let the tool do the work!”* - so.. the reason why we quickly came to realize just how wise this initially irritating/inane advice really was, is because according to the laws of physics work-energy theorem: We only do the work of changing the kinetic energy of the tool, but only the tool’s energy of motion can now do “the work”.. so ya, let the tool do the work!
Thank you so much Sir!!! I learn a lot from you!!! You're a blessing to students just like me who can't easily catch up with what their professors where teaching! Again, Thank you so much!! ❤
Thank you Mr. Dave, this is such a great summary; simply packed (?) and brief. I would like to share this on physics class. Please do continue doing this sort of video, you really did help me with many of my assignments at school, I often come back watching your videos if I need help on what kind of phrasing should I use to be more understandable. Also, the jokes. It's great.
The second law of thermodynamics (part of it) is that all physical processes create entropy and entropy the amount of energy not available to do work. It, along with the first law is the reason you can't create a perpetual motion machine, all the energy will "turn useless" which is the second part, that all the energy will become entropic in a closed system. Still trying to figure out entropy so that's why I bring this up.
So, if take the perpetual motion machine example, say a machine that (well, it doesn't succeed obviously) that is a closed system and tries to recycle the energy into itself, stops working, how? It's able to do it, initially, but then eventually it can't, what is going on? I'm trying to think of an example of something we could try to make into a perpetual motion machine that would obviously fail to do so, so I can try to figure it out. I'd say water that falls turning a wheel, in which the wheel pumps the water back up to fall on itself to turn it, but that's not exactly closed, because what starts the wheel turning in the first place?
A perpetual motion machine could exist in theory, if you were able to eliminate all losses, such as friction, viscosity, drag, and ohmic resistance. But the minute you try to extract any energy out of it for any application at all, it will no longer be in perpetual motion. You will slow down the motion, and deplete its energy. What people really mean by "a perpetual motion machine", is really a more like a perpetual WORK machine. A machine that can continuously deliver a work output, without any work input. It doesn't exist in reality. A planet in orbit around a star is one example of what would technically be a perpetual motion machine by the direct meaning of the words. But if you were to extract work out of the orbital speed of the planet to power your own machine, the planet will not keep orbiting at the same position. Its orbital energy will decrease, and its orbital radius (or more generally, semimajor axis) will also decrease. Continue extracting energy, and it will end up on a crash trajectory with the star.
You will notice that when theta equals zero, cosine of theta reduces to 1. Thus you will get the same answer as if you had calculated W=F*d*cos(theta), or W=F*d itself. The full generalized form of the work definition equation is: W = integral F dot dx where F is a vector at every point along the way, and dx the various infinitesimal displacement vectors that add up to the full path length. This reduces to a single dot product of force dot displacement (W = F dot d) when the force is constant at every point along the way, and the displacement is a simple straight line. The dot product is a special kind of multiplication that multiplies the aligned components of two vectors, hence the cosine term that develops. Since d already has another full time job in Calculus, it is common to use another letter to indicate displacement, such as x or s.
The definition of work in Physics as what happens when an applied force causes a displacement of an object is completely erroneous or wrong and work ,hence, is not really force times displacement(F•d). Work is a vector quantity(i.e. it's not a scalar) and ,in general, is defined as a "physical-displacement(ms)" by or due to a force, an impulse, or a kinetic force. The work-energy theorem stating that the net work done on an object equals the change in the kinetic energy of the object is completely erroneous or wrong too. It would be the net force on an object that is equal to the change in the kinetic energy of the object.
Not necessarily. That is true if the NET work done on the object is negative, but not just the work in general. Consider the example with you and your baby brother, both pushing a box. You push forward on it, and your baby brother being a little brat, pushes backwards on the box. Your baby brother is doing negative work on the box, but you are doing positive work on the box. It is possible that the both of you increase the speed of the box as a net result, because you do a lot more work than your baby brother. The net work is positive, even if your baby brother's contribution is negative and counterproductive to your effort.
Mr.Dave,in a previous video, you explained that scalers don't have negative magnitude, could you clarify how work has a positive and negative magnitude although it is considered as a scaler, plz?
Some scalars can be negative. Some make no sense for them to be negative. Some examples of scalars that can be negative: Work Potential energy Voltage Current Power Divergence Money (e.g. debt) Electrical charge Outputs of trigonometry functions Some examples of scalars that make no sense to have negative values: Speed Distance Length Volume Mass Kinetic Energy Coefficient of restitution Coefficient of friction Temperature in the absolute scales of Kelvin and Rankine
Do you have videos for conservation of momentum, radial acceleration, potential and kinetic energy equation examples? Please it would help a lot with physics
When we apply force to an object it'll cover infite distance (1st law of motion) but it actually nor happens due to friction so technically friction opposed the force we applied so how does it related to energy ? You doing the same work on rough surface and plan surface so how does you get kore tired there since you apllied the same energy
When you have that girl you like that isn't for you and no matter how much mass of effort and acceleration of your quickness in action to try to captivate her before anyone else, but she still ends up with your best friend, YOU TWO WILL NEVER WORK.
This lesson confused me. Work is equal to (magnitude of force) * (D) is it distance or displacement (ik their differences but you interchange them at 1:08 ) and you said work is scalar if the "D" in W=(F)(D) is displacement (thats what you and my professor said) then why is work a scalar quantity and not a vector quantity Especially when you apply work on an object by an angle in which you must use a cos(x)
Work is the product between magnitude of force and magnitude of displacement. More technically, it's the dot product between force and displacement. So obviously work is a scalar quantity! Hope it helps
It is displacement. That is why the cosine(theta) develops in the equation. You are taking a dot product of force and displacement, as opposed to just a scalar multiplication of distance and force. When the vectors are aligned, you get away with ignoring the fact that it is really displacement, and just multiplying magnitudes. But when vectors are not aligned, that's when you need to consider the cosine term to account for direction. Or you can use the "multiply corresponding components and add up the products" strategy of taking a dot product.
If we push an object in space and that object keeps accelerating assume it gets infinite velocity at infinite displacement..we get work as F*infinity....which will be very large offcourse (infinite ) here kinetic energy Is also increasing and work is also being done....how is it possible that work is done and energy is gained !
I have a question professor Dave if you push the box at 90° and the box moves downward then the applied force is now parallel to the displacement of the object, I think there is work done given the definition of work
In this example, the box doesn't move downward, because it is constrained by the normal force from the floor. Assume we are talking about a rigid box and a rigid floor, rather than a compressible cardboard box.
Actually theta is the angle between force and displacement.In your situation the angle between force and displacement is still cos 0 as they are parallel to each other.remember that theta is not only the angle of force it is the angle between force and displacement
Thank you soooooo much for making these videos. I know you have helped tons of students understanding the subjects more.
ruclips.net/video/Vw8U2dW03eY/видео.html
😀😃😃😄😍😆🙂😊😇🥰😍🤩😘😗
intro: professor so kiddish
video: very serious
We are trying to learn and you here doing memes😂
truth
riggght ....but also he looks so jewish too
Maot kaayo
@@ezzo3788 😂😂😂😂
This man just summed up 3 hours of me reading the textbook in about 5 minutes... Truly good stuff and easy to understand. Thank you Hendy
"Colloquial connotations." Love it. It's a polite way of saying, "Don't embarrass yourself."
thanks dad
Ur welcome
@@DudeWhoSaysDeez no your patrick
What is he u r dad 😀😀That seems to be weird
@@devendrareddy816 hes ur dad as well.
He is Jesus
The introduction of cosine and its values influencing the amount of work really blew my mind for some reason. Being able to quantify things like that really makes me appreciate this crazy universe. These videos are immensely valuable and you are one of the reasons I have chosen to pursue an education in physics
It's not mind-blowing 😅
You know you never really use too many examples or if you do they are simple, but honestly that should be the way they initial teach. It really helps me understand where things come from before practicing the actual examples later.
Hello, This guy actually teaches you more in 5 minutes than your teacher in an entire semester.
Thank you smmmm!!! You're honestly physics Jesus who's going to help me more than my physics teacher ever will for HSC
I felt bamboozled knowing that this is the first video that I’ve seen that did not include comprehension in the end. But nonetheless you’re explanation are always superb thank you very much!
legit the most helpful channel ive ever encountered for my physics class
Dear Dave: my appreciation for this excellent , simple and interesting explanation
I didn't know Dave Grohl knew so much about Physics!
thanks very much for the explanations i am having a test tomorrow about work and energy and i feel much clever after i watched this video and i like the way you explain work and energy i cant wait to see more of your videos about KE and PE thanks for the video now even my sister carly can understand
5 years too late - but I hope the test went well for you.
Okay. So here is a very fundamental doubt.
We know that work = energy. (It definitely is. Because,
work=fd= 1/2mv(v)= energy
And energy is the ability to do work..(1)
That implies
Work=ability to do work (using (1))?😮😮
How can two things which are exactly equal can be different from each other?
This is so helpful it covered all that I needed for my quarter exam
im so happy i found a youtuber that can help me with bioligy,chemistry and physicis this means so much to me.. u have no idea how ur helping me with my finals :)
I am learning a lot from you Professor Dave! Thank you so much po!
In physics, "work" is when a force applied to an object moves the object in the same direction as the force. If someone pushes against a wall, no work is done on the wall because it does not move. However, depressing a letter on a computer keyboard requires work.
I've never understood these problems without you, thank you very very much bro. You're my professor. ❤ love frome 🇹🇭 🇹🇭 🇹🇭 🇹🇭.
Hi, i am a student in grade six. Can you please explain what theta, cos and work-energy theorm? Thank you 🙏🏻
check out my mathematics playlist! or more specifically my trigonometry playlist.
Theeta is a greek letter, just like we use 'x' and 'y' to mark angles. Cos theeta means the effect of that force in the horizontal direction. For example if you hit a football in north-east direction, actually it had travelled in two perpendicular directions, north and east...the force which contributed for the force only to travel to east means Fcos(theeta)..its something like that..... And work energy theorem means that, the more energy u have, the more u can transfer it and do work...just like if u have more money, you can spend to buy more things and vice versa.. in physics, that spending to buy part should be replaced by 'making an object move'(do work)
after watching his video for 3 times with the video from CrashCourse 2 times now i understand it with a smile face. We love you Pro Dave
My man getting me right! We all appreciate your hard work.
This makes me think of the old expression every young man is scolded/initiated with into the world of manual labor:
*”Let the tool do the work!”* - so.. the reason why we quickly came to realize just how wise this initially irritating/inane advice really was, is because according to the laws of physics work-energy theorem: We only do the work of changing the kinetic energy of the tool, but only the tool’s energy of motion can now do “the work”.. so ya, let the tool do the work!
bruh do we rly need this shit for life
This is so perfect. I needed something that teaches me how to do problems but in a very easy and fun way.
Thank you so much Sir!!! I learn a lot from you!!! You're a blessing to students just like me who can't easily catch up with what their professors where teaching! Again, Thank you so much!! ❤
Professor Dave is awesome, thank you so much
Matt Z Ditto. Great way to understand what energy is.
it is really big help to me. thank you
Baby brother is pushing you with 1newton force and final work is 6N.m
Once again dude thank you
Am starting to love his ways😭❤️ specifically the introduction 🙌🤣🤣
Belated Happy Teachers Daaaaaaaaaaaayy~!
Thank you Professor Dave 👍👍👍
But, F=ma, W=Fd, W=dma, W=dmd/t², W=m×d²/t², W=m×v²
KE=0.5mv²
W=mv²
W=2×KE
?W=∆KE
∆KE=KE1-KE2
What is going on, please help.
Why is it only half of an objects mass in the formula for Kenetic Energy?
This really helped me prepare for my test.
You are my best teachers sir
Thanks for this video, Professor. A blessed day, everyone!
Thank you Mr. Dave, this is such a great summary; simply packed (?) and brief. I would like to share this on physics class.
Please do continue doing this sort of video, you really did help me with many of my assignments at school, I often come back watching your videos if I need help on what kind of phrasing should I use to be more understandable.
Also, the jokes. It's great.
1: 45 andddd 2:33
omg, i wish my teacher could explain physics like you! i'm gonna drop outttt.....loollllz
i love you P. Dave
Love the intro.. 💫💫
Sir as u said, work may be positive or negative..
But work is a scalar quantity
we just use positive and negative values to distinguish between work done on a system and work done by a system.
The second law of thermodynamics (part of it) is that all physical processes create entropy and entropy the amount of energy not available to do work. It, along with the first law is the reason you can't create a perpetual motion machine, all the energy will "turn useless" which is the second part, that all the energy will become entropic in a closed system. Still trying to figure out entropy so that's why I bring this up.
yep it's a multifaceted law! can be expressed in a variety of ways.
So, if take the perpetual motion machine example, say a machine that (well, it doesn't succeed obviously) that is a closed system and tries to recycle the energy into itself, stops working, how? It's able to do it, initially, but then eventually it can't, what is going on? I'm trying to think of an example of something we could try to make into a perpetual motion machine that would obviously fail to do so, so I can try to figure it out. I'd say water that falls turning a wheel, in which the wheel pumps the water back up to fall on itself to turn it, but that's not exactly closed, because what starts the wheel turning in the first place?
A perpetual motion machine could exist in theory, if you were able to eliminate all losses, such as friction, viscosity, drag, and ohmic resistance. But the minute you try to extract any energy out of it for any application at all, it will no longer be in perpetual motion. You will slow down the motion, and deplete its energy.
What people really mean by "a perpetual motion machine", is really a more like a perpetual WORK machine. A machine that can continuously deliver a work output, without any work input. It doesn't exist in reality.
A planet in orbit around a star is one example of what would technically be a perpetual motion machine by the direct meaning of the words. But if you were to extract work out of the orbital speed of the planet to power your own machine, the planet will not keep orbiting at the same position. Its orbital energy will decrease, and its orbital radius (or more generally, semimajor axis) will also decrease. Continue extracting energy, and it will end up on a crash trajectory with the star.
AP exam this Friday thank you professor Dave 👍👍👍👍
I'm a bit confused on when to use W=Fd vs. W=Fdcostheta
first one if force is applied in direction of motion and second one if at an angle
You will notice that when theta equals zero, cosine of theta reduces to 1. Thus you will get the same answer as if you had calculated W=F*d*cos(theta), or W=F*d itself.
The full generalized form of the work definition equation is:
W = integral F dot dx
where F is a vector at every point along the way, and dx the various infinitesimal displacement vectors that add up to the full path length. This reduces to a single dot product of force dot displacement (W = F dot d) when the force is constant at every point along the way, and the displacement is a simple straight line. The dot product is a special kind of multiplication that multiplies the aligned components of two vectors, hence the cosine term that develops.
Since d already has another full time job in Calculus, it is common to use another letter to indicate displacement, such as x or s.
Clearly explained. Thank you
thank u dave 🤘 my advisor makes me watch these videos and as much as i hate working i learn a lot in these videos
Very good Professor Dave
Thank you very much professor Dave, I had a lot of doubts but after watching this. It all makes sense now, thanks again!
Thanks for your video, you explain it very well and in a short amount of time
Wow! your's voice is superb
Sir your teaching method is very easy and outstanding 🙏🙏🙏👍👍👍👍
I like the intro very much
I love your tutorial sir
Excellent explanation.
Thank you !
The definition of work in Physics as what happens when an applied force causes a displacement of an object is completely erroneous or wrong and work ,hence, is not really force times displacement(F•d). Work is a vector quantity(i.e. it's not a scalar) and ,in general, is defined as a "physical-displacement(ms)" by or due to a force, an impulse, or a kinetic force.
The work-energy theorem stating that the net work done on an object equals the change in the kinetic energy of the object is completely erroneous or wrong too. It would be the net force on an object that is equal to the change in the kinetic energy of the object.
Thank you so much 🎉
Thank you so much ! Really appreciate it ❤
You just got a new sub
what if we lift the box, would it make the work 0? because Fdcos90 is 0, that means w =0?
what a king, thank you
my teachers' so lazy that she just tells us to search the lessons at home : /////
WutFace
That’s a terrible teacher our teacher gives us a book and notebooks and tells us its do tomorrow
Uhhhh same 😑😞
she was prepping you for the apocalypse
Lmao basically online class
He is amazing.... Want more
thank you. God bless
clearly explained!
Dev is genius
thank you dave
Thanks for being a good teacher or that you're acquiring incorrect knowledge because that's what it is.
So if the work is negative that means the speed will decrease and vice versa right ? Does it works every time ?
Not necessarily. That is true if the NET work done on the object is negative, but not just the work in general.
Consider the example with you and your baby brother, both pushing a box. You push forward on it, and your baby brother being a little brat, pushes backwards on the box. Your baby brother is doing negative work on the box, but you are doing positive work on the box. It is possible that the both of you increase the speed of the box as a net result, because you do a lot more work than your baby brother. The net work is positive, even if your baby brother's contribution is negative and counterproductive to your effort.
Watching this but I know I’m still going to fail my AP Physics exam lol
did you pass, how should i survive if i fail
SHAAN KUMAR what did u get??
Don't worry , believe in physics jesus
@@kawaichanx3 thats a holy name bruh
Thank you ser for helping me out
thank you professor
Thanks!
The real father of physics.
why shouldnt we consider the y-components when caculating work??
Omg you are literally god thank you so much😭❤️
Thank you 👍👍👍
Of which branch of Physics these concepts are????
Mechanics
Mr.Dave,in a previous video, you explained that scalers don't have negative magnitude, could you clarify how work has a positive and negative magnitude although it is considered as a scaler, plz?
Some scalars can be negative. Some make no sense for them to be negative.
Some examples of scalars that can be negative:
Work
Potential energy
Voltage
Current
Power
Divergence
Money (e.g. debt)
Electrical charge
Outputs of trigonometry functions
Some examples of scalars that make no sense to have negative values:
Speed
Distance
Length
Volume
Mass
Kinetic Energy
Coefficient of restitution
Coefficient of friction
Temperature in the absolute scales of Kelvin and Rankine
Do you have videos for conservation of momentum, radial acceleration, potential and kinetic energy equation examples? Please it would help a lot with physics
check out my classical physics playlist it's all in there!
Thanks very much pro
I attend your videos always and I got more knowledge from your teaching.
you are such a great teacher, thanks for your effort
Any comments pls ruclips.net/video/Vw8U2dW03eY/видео.html
When we apply force to an object it'll cover infite distance (1st law of motion) but it actually nor happens due to friction so technically friction opposed the force we applied so how does it related to energy ? You doing the same work on rough surface and plan surface so how does you get kore tired there since you apllied the same energy
we all luv u professor dave
He may very well be a good professor, but it's really incorrect knowledge.
Did u say work is scalar?😮
Nice sir
2:55 When you give your sibling an unplugged controller
Subscribeb, this helps me a lot. Have a quiz tmr, fingers crossed 🤞
Thankful professor ❤💜
When you have that girl you like that isn't for you and no matter how much mass of effort and acceleration of your quickness in action to try to captivate her before anyone else, but she still ends up with your best friend, YOU TWO WILL NEVER WORK.
This lesson confused me. Work is equal to (magnitude of force) * (D)
is it distance or displacement (ik their differences but you interchange them at 1:08 )
and you said work is scalar
if the "D" in W=(F)(D) is displacement (thats what you and my professor said) then why is work a scalar quantity and not a vector quantity
Especially when you apply work on an object by an angle in which you must use a cos(x)
Work is the product between magnitude of force and magnitude of displacement. More technically, it's the dot product between force and displacement. So obviously work is a scalar quantity! Hope it helps
It is displacement. That is why the cosine(theta) develops in the equation. You are taking a dot product of force and displacement, as opposed to just a scalar multiplication of distance and force.
When the vectors are aligned, you get away with ignoring the fact that it is really displacement, and just multiplying magnitudes. But when vectors are not aligned, that's when you need to consider the cosine term to account for direction. Or you can use the "multiply corresponding components and add up the products" strategy of taking a dot product.
i love the intro
thank you
A lot of love to you Mr Dave from India
If you don't understand,it's probably coz your looking at professor Dave the whole time...
Happened to me!
thanks dude
Arigathanks Otosan
If we push an object in space and that object keeps accelerating assume it gets infinite velocity at infinite displacement..we get work as F*infinity....which will be very large offcourse (infinite ) here kinetic energy Is also increasing and work is also being done....how is it possible that work is done and energy is gained !
Pls stop discovering. I've had enough of physics history
Good Explaination. @
I have a question professor Dave if you push the box at 90° and the box moves downward then the applied force is now parallel to the displacement of the object, I think there is work done given the definition of work
In this example, the box doesn't move downward, because it is constrained by the normal force from the floor. Assume we are talking about a rigid box and a rigid floor, rather than a compressible cardboard box.
Actually theta is the angle between force and displacement.In your situation the angle between force and displacement is still cos 0 as they are parallel to each other.remember that theta is not only the angle of force it is the angle between force and displacement