Why does an object have kinetic energy even when it's not moving?

AI Thread Summary
Kinetic energy is dependent on the reference frame of the observer, meaning that an object can appear to have kinetic energy even when stationary in one frame. For example, a ball held in a moving car has no kinetic energy relative to the car's occupant but has significant kinetic energy relative to a stationary observer on the ground. This illustrates that kinetic energy is not absolute; it varies based on the motion of the observer. The concept emphasizes that there is no such thing as absolute kinetic energy. Understanding this principle is crucial for grasping the nature of motion and energy in physics.
courtrigrad
Messages
1,236
Reaction score
2
Hello all

I was just wondering if an object is stationary, how can it still possesses kinetic energy? Is it due to the reference frame? Does everything possesses kinetic energy?

Thanks
 
Last edited:
Physics news on Phys.org
any ideas?
 
you are right, kinetic energy depends on the reference frame, how? let me show you an example.
lets say you are in a car which traveling 60mile/hr, and holding a metal ball STATIONARY on your hand, for you, the ball has no kinetics energy, but for me (who standing on the ground), the ball carries a huge kinetics energy, how to prove it? easy, when your car passes by me, throw the ball out and see how much demage the ball will do...
conclution: the kinetic energy is depended on the motion of the observer, there are no such thing call absulote kinetic energy,
 
thanks a lot

just a test:

a^{2}+\frac{1}{a^{2}}+2(a+\frac{1}{a})=7
 
Last edited:
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »
Thread 'A cylinder connected to a hanged mass'

Thread 'A cylinder connected to a hanged mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

A cylinder rotating on a plane with friction and then moving across a frictionless plane to a collision
Replies
1
Views
740
Kinetic Energy of a Cylinder Rolling Without Slipping
Replies
21
Views
4K
Resistance force changing the velocity of an object
Replies
8
Views
1K
Why does an electron have minimum kinetic energy when its momentum is 2h/λ?
Replies
8
Views
2K
Conservation of Energy with Gravitational Potential Energy
Replies
6
Views
2K
Friction and an object stopping
Replies
12
Views
2K
Minimal rotational kinetic energy for a gyroscope to precess
Replies
33
Views
2K
Internal energy of a gas and kinetic energy, "typical velocity"
Replies
5
Views
754
When does an object have kinetic rotational energy?
Replies
8
Views
2K
Why can we move the spring with constant speed when we apply a force?
Replies
29
Views
2K

Hot Threads

Recent Insights

Back
Top