Tell Me About Kinetic Energy, Please

In summary, the conversation is discussing kinetic energy and its relationship to force and velocity. It is mentioned that according to traditional physics, kinetic energy is calculated using the equation E=mVV/2, which shows that when speed is constant and nonzero, there is no change in energy. It is also stated that according to Newton's first law, when speed is constant, the resulting force acting on the object is zero. The conversation also delves into the concept of work done and how it relates to the change in energy. It is ultimately concluded that when force is constant, there is no change in energy. The conversation also touches on the use of different notations and the paradox of kinetic energy for objects with constant speed.
  • #1
dock
Tell Me About Kinetic Energy, Please!

according to the traditional physics the kinetic energy is:

E=mVV/2;

let that speed be constant and nonzero => E<>0;

according to Newton the 1st whenevr the speed V=const the resulting force acting upon that object is zero;

the energy by definition is:
E=FxX;

since F=0 => E=0

HOW ABOUT THAT?
 
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  • #2
Erm... no?

Work done = change in energy is the integral of force with respect to distance.

All this shows is that there is no change in kinetic energy for an object moving at constant velocity.
Which is obvious, really.
 
  • #3
And use * instead of x for the multiplication operator. It's less confusing that way.
 
  • #4
Originally posted by FZ+
Erm... no?

Work done = change in energy is the integral of force with respect to distance.

All this shows is that there is no change in kinetic energy for an object moving at constant velocity.
Which is obvious, really.
i'm not talking about dE but E.
OK so dE=FdX then integrated we have (E=FX and F=const)
d(E=FX) <=> dE=FdX cause F=0=const.
so it's not only dE=0 but E=0 also!

when F=const then dE=FdX
when E=const then FdX=-XdF
when X=const then dE=XdF
when none then
dE=FdX+XdF

supportive members, please, be louder!
 
  • #5
Let me repeat:

YOU HAVE SHOWN THE CHANGE IN ENERGY.

YOU HAVE SHOWN THERE IS NO CHANGE IN ENERGY.

F * x = Work Done = change in energy

Integral of F wrt x gives F*x + C

The constant of integration C is the initial kinetic energy of the system.

UNDERSTOOD?
 
  • #6
Originally posted by FZ+
Let me repeat:

YOU HAVE SHOWN THE CHANGE IN ENERGY.

YOU HAVE SHOWN THERE IS NO CHANGE IN ENERGY.

F * x = Work Done = change in energy

Integral of F wrt x gives F*x + C

The constant of integration C is the initial kinetic energy of the system.

UNDERSTOOD?
F * x = Work done?
ain't Work done = dE?
how come only one derivate in that equation.that violates the mightiest of the laws:"Every change is simultaneous with at least one other".
& int Fdx = F(x(2)-x(1))
but it's also
& int dE = E(2)-E(1)
and then
E(2)-F(2)x(2)=E(1)-F(1)x(1)=const=0 threrefore

E=Fx

cause

F(1)=F(2)=F
you cannot put starting condition on the staring conditions.it leads no where that's whay that const=0.
 
  • #7
Its just different notations in different equations, dock. Apparently wherever you got that from uses dE and E interchangeably. And its not unreasonable to do so since often times a change in E results in a conversion from one form of E to another (such as kinetic being converted to potential).
 
  • #8
dock, from the Work-Energy theorom, the change in energy in a system is equal to the work.
So F*x (the work) is equal to dE in the system.
E(2)-F(2)x(2)=E(1)-F(1)x(1)=const=0 threrefore
It is right that when F=0, E=const, but why are you taking this const to be 0 ?
 
  • #9
this kinetic energy paradox aplies to the photon as well.
the photon has constant speed c => the force is zero => the energy of the photon is zero cause E=FxX=0xX=0.
 

What is kinetic energy?

Kinetic energy is the energy an object possesses due to its motion. It is a form of energy that is associated with an object's mass and its velocity.

How is kinetic energy calculated?

The equation for kinetic energy is KE = 1/2 x mv^2, where m is the mass of the object and v is its velocity. This means that the greater the mass and velocity of an object, the more kinetic energy it will have.

What are some examples of kinetic energy?

Examples of kinetic energy include a moving car, a thrown baseball, and a person running. Essentially, any object that is in motion has kinetic energy.

What is the difference between kinetic and potential energy?

Kinetic energy is the energy of motion, while potential energy is the energy that an object possesses due to its position or condition. In other words, kinetic energy is present when an object is in motion, while potential energy is stored and can be converted into kinetic energy.

How is kinetic energy important in everyday life?

Kinetic energy plays a crucial role in our everyday lives. It is the energy that powers transportation, from cars to airplanes. It also powers machines and appliances, such as blenders and washing machines. Kinetic energy is also important in sports, as it is what allows athletes to run, jump, and throw. Additionally, kinetic energy is essential for producing electricity through turbines and generators.

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