Like searched the internet and everyone is saying that it is an energy due to speed or something but like I don’t get it. How can something like kinetic energy exists if there is no such thing as speed( I think like speed is no such thing as gravitation or nuclear speed is something else it is not similar like nuclear or gravity)
In: Physics
It’s not speed, it’s velocity, and velocity is a real thing. Velocity is the movement of matter.
When you throw a rock at a window and shatter the window, the energy required to break the window came from the kinetic energy of the rock.
The faster you throw the rock, or the more mass the rock has (ie a bigger more massive rock) the more kinetic energy the rock has.
It sounds like you’re getting a bit confused; while there is no absolute velocity, there is also not any absolute energy. It’s always measured in relation to something
Not sure what you mean by “no such thing as speed”. Momentum is most certainly a thing, and that is related to mass and speed of an object.
I think what you mean is that speed isn’t a force. Which is true. Speed is just a way energy manifests. Forces are ways to move energy around.
Kinetic energy is just the energy contained in an object. You can change it by applying a force to it. For example, hitting the object with another moving object will change its kinetic energy. The force involved is the electromagnetic force since that is the force responsible for objects not moving through each other.
Kinetic energy derives from velocity. Velocity is a change of position over time, with a particular direction. E.g. if you walk two meters east, over one second, that would be a velocity.
Velocity, usually denoted “v”, measures how displacement (position where you care about direction) changes over time. Kinetic energy, by definition, is equal to 1/2×m×v^2 and represents the amount of energy “stored” in the motion of that object. Another way you could think of it is: How much energy, aka “work,” would you have to do, in order to make that moving object come to a complete standstill. The kinetic energy of a body is that energy.
We actually use kinetic energy as a storage medium in real life, too! Specifically in devices called flywheels. You can spin up a flywheel so that it’s going really, really, *really* fast, and then use that spinning speed to power other devices. That slows the wheel down, until eventually it runs out of rotational kinetic energy, coming to a stop. They are used in places that need smaller energy storage and don’t mind the occasional spin-up or replacement.
Pendulums and springs are other examples of systems that alternate between kinetic energy and potential energy. When a spring is compressed, it has a lot of elastic potential energy stored in it. If you attach a spring to the ceiling, stick a weight on the end, and let it bounce, it will oscillate back and forth, changing between having the spring compressed or stretched (=elastic potential energy) and having the weight moving downward or upward with the spring (=kinetic energy). Note that, even though velocity can be negative, kinetic energy cannot, because you square the velocity term, and thus remove any negative sign it might have.
The important thing is not to think of energy as something tangible like mass. An object isn’t glowing and buzzing filled with kinetic energy. It’s just a mathematic quantity, it doesn’t “exist” as such.
What it describes is, if I were to slow this object down to a standstill, how much work could I make it do? E.g. by letting it push a turbine.
Clearly “standstill” refers to a frame of reference. If you move along with the object, from your point of view you cannot make it do any work and it therefore it has no kinetic energy *to you*. It’s all relative.
Latest Answers