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

[courtrigrad]

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

 

[courtrigrad]

any ideas?

 

[vincentchan]

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,

 

[courtrigrad]

thanks a lot

just a test:

$$a^{2}+\frac{1}{a^{2}}+2(a+\frac{1}{a})=7$$