Kinetic Energy Equation/Simple Explanation?

Click For Summary

Discussion Overview

The discussion revolves around the concept of kinetic energy, specifically the equation EK=1/2mv^2. Participants express confusion about the meaning and derivation of the equation, seeking a clearer understanding of kinetic energy and its implications.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant expresses confusion about the kinetic energy equation and requests a simple explanation of its meaning and derivation.
  • Another participant points to an external article for derivation information.
  • Some participants assert that kinetic energy represents the work required to accelerate an object from rest to its current speed, noting that this is true in the absence of friction or other dissipative forces.
  • A participant elaborates on the relationship between mass, velocity, and kinetic energy, explaining that a more massive object or a faster-moving object has more kinetic energy.
  • One participant discusses the squared relationship of velocity in the equation, suggesting that it reflects the increased difficulty in accelerating to higher speeds and the implications for stopping distances.
  • Another participant provides an analogy involving a shopping cart to illustrate the concept of kinetic energy in relation to work done to stop an object.
  • Several participants acknowledge each other's points, with one explicitly stating that they are not correcting others but rather clarifying their own understanding.

Areas of Agreement / Disagreement

Participants generally agree on the basic concept of kinetic energy as related to work and speed, but there is no consensus on the derivation or deeper implications of the equation itself. Multiple viewpoints and explanations are presented without resolution.

Contextual Notes

Some assumptions about the absence of friction and the conditions under which kinetic energy is defined are mentioned, but these are not universally accepted or elaborated upon in detail.

agentsanta
Messages
10
Reaction score
0
Ok, so I sort of have an idea of what kinetic energy is but I'm still kind of confused. I'm confused mainly because of the equation. Every source I've gone to has just given me the equation
EK=1/2mv^2
but none of the sources mentions where it came from or what it means
It almost seems like someone just pulled it out of thin air o.O
Could someone give me a simple yet effective explanation of what Kinetic Energy is and the meaning/derivation of that formula?
Thx in advance ^.^
 
Physics news on Phys.org
KE is the amount of work required to get an object from rest to its current speed.
 
DaleSpam said:
KE is the amount of work required to get an object from rest to its current speed.
In the absence of friction or other dissipative forces. In other words, it is the amount of work done on an object moving at speed v, with mass m.
 
Good point, thanks for the clarification.
 
DaleSpam said:
Good point, thanks for the clarification.
Just to make sure: I wasn't correcting or providing clarification for you :redface:, I wouldn't dream of doing that.
 
It's pretty straight forward if you think about it.

The m is mass...obviously a train, being more massive, will have more energy than a car traveling at the same speed.

The v is velocity. Again, obviously a faster moving car will have more energy than a slower moving car. If it hits a wall, it will get more deformed, it takes longer to stop, etc.

The velocity is squared because it's much harder to accelerate a car to 40mph than to 20mph. 4x harder, to be precise.

Might not make sense at first, but if you jump out of a 2nd floor window you will NOT hit the ground twice as fast as from a 1st floor window (assuming the 2nd floor is 2x higher than the 1st). It's because the higher you jump, the faster you go and the less time gravity has to pull you down. You actually have to jump from the 4th floor in order to let gravity pull on you twice as long, and to hit the ground twice as fast (and 4x harder). Don't jump out of windows, but you can drop stuff down to convince yourself of this.

Works the same with cars and everything else...you need to accelerate through 4x the distance to go 2x as fast. Braking, too...you need 4x more road to brake from 100mph as from 50mph.

I don't know what's up with the 1/2 mv^2. Either way, the point remains that energy is proportional to how much mass you have, and exponentially proportional to how fast you're going. That's all the equation is saying. It by no means is pulled out of thin air.
 
DaleSpam said:
KE is the amount of work required to get an object from rest to its current speed.

Or equivalently, the amount of work required to completely stop an object that is moving as some speed. Think about trying to stop a shopping cart coming at you by holding out your hand. If the speed is greatly, the cart has more kinetic energy, and you will have to do more work to stop it. If its mass is greater (it's filled with watermelons), again, it will have more kinetic energy and will require more work to stop.
 
Sorry for the late reply I was a little busy
Thx for all the replies, I get it now
 

Similar threads

Undergrad How can we prove the kinetic energy equation
  • · Replies 2 ·
Replies
2
Views
2K
High School Curious about the work - energy theorem
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad Same old question, I still don't get it: E=1/2mv^2 - more E with V?
  • · Replies 41 ·
2
Replies
41
Views
4K
Undergrad I am confused about the meaning, and value, of kinetic energy
  • · Replies 7 ·
Replies
7
Views
2K
High School About verification on Kinetic energy and work
  • · Replies 16 ·
Replies
16
Views
4K
Undergrad Question about Momentum vs. Kinetic Energy vs. Deforming In Collisions
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Bernoulli's equation and the work energy theorem
  • · Replies 21 ·
Replies
21
Views
3K
High School Colliding balls: Conservation of momentum and changes in kinetic energy?
  • · Replies 2 ·
Replies
2
Views
2K
High School Conceptually understanding change in potential energy with 0 net work
  • · Replies 9 ·
Replies
9
Views
3K
Undergrad Work Done/Energy Transferred in One Dimensional Collision
  • · Replies 5 ·
Replies
5
Views
2K