- #1
Melac12
- 6
- 0
When my textbook talks about energy it starts with kinetic and potential. The derivation goes like this. F=ma=m(dv/dt)=-mg then they split the derivative using chain rule
(dv/dt)=(dv/dy)(dy/dt) therefore since (dy/dt)=v we get F=mv(dv/dy)=-mg then they write mv dv= -mg dy then they integrate ∫mv dv= -∫mg dy and we get
(1/2)(mv^2)-(1/2)(mv^2)=-(mgy)+(mgy)
Then the textbook just defines kinetic and potential energy and says that J=1kg(m/s)^2
I have a hard time understanding why they did this things. If I were a scientist what would make me do all those steps then integrate and then define energy with that unit. What made them think that that derived unit represents energy? How do they know they are right? Energy is not something we see like motion and its not something we feel like force, but we know its there. And clearly energy is related to force so how did scientists put it all together?
If anyone can explain to me why this is a good way to define energy and perhaps also tell me how scientists got to it historically, it would be greatly appreciated.
(dv/dt)=(dv/dy)(dy/dt) therefore since (dy/dt)=v we get F=mv(dv/dy)=-mg then they write mv dv= -mg dy then they integrate ∫mv dv= -∫mg dy and we get
(1/2)(mv^2)-(1/2)(mv^2)=-(mgy)+(mgy)
Then the textbook just defines kinetic and potential energy and says that J=1kg(m/s)^2
I have a hard time understanding why they did this things. If I were a scientist what would make me do all those steps then integrate and then define energy with that unit. What made them think that that derived unit represents energy? How do they know they are right? Energy is not something we see like motion and its not something we feel like force, but we know its there. And clearly energy is related to force so how did scientists put it all together?
If anyone can explain to me why this is a good way to define energy and perhaps also tell me how scientists got to it historically, it would be greatly appreciated.