Answer Kinetic Energy Questions About an Asteroid Moving in Space

[sponsoredwalk]

Hi I just have a quick question about Kinetic Energy.

If we imagine an asteroid in empty space with no gravity field acting on it, i.e. it's just in empty space moving along according to Newtons 1st Law i.e. with constant velocity.

Imagine a ship extends a magical robotic hand and exerts a force on the asteroid for a few seconds before letting it go, I want to know what happens.

I would say that because K_2 - K_1 = ½mv² - ½mv_0² = Fd the asteroid will have a higher kinetic energy at the end when the robotic arm let's go.

1: But, say an hour later, the asteroid will still be moving forward, will it still have the same kinetic energy as it did when it was released from the robotic arm?
No force is acting on it so no work is done but does the asteroid still have kinetic energy?

2: Also, if I use the kinetic energy as the asteroid is moving, well after it has been released, I will get the answer that the ship has no kinetic energy, what is wrong here?
Does something have kinetic energy only while a force acts on it?

I know it will have momentum as it moves but what about kinetic energy?

 

[cepheid]

1: But, say an hour later, the asteroid will still be moving forward, will it still have the same kinetic energy as it did when it was released from the robotic arm?

Yes. Energy is conserved. It doesn't just disappear.

No force is acting on it so no work is done but does the asteroid still have kinetic energy?

The work done is equal to the CHANGE in kinetic energy. If no work is done, the kinetic energy will remain the same. It won't change. That's why it will be exactly the same one hour later.

2: Also, if I use the kinetic energy as the asteroid is moving, well after it has been released, I will get the answer that the ship has no kinetic energy, what is wrong here?

I don't understand what you mean. Can you explain more clearly what exactly you are trying to compute?

Does something have kinetic energy only while a force acts on it?

No, a force is not required! As the formula for kinetic energy that you posted clearly shows, if something has velocity, it has kinetic energy. Kinetic means "having to do with motion", and kinetic energy is the energy associated with motion. If something is moving, it has kinetic energy.

 

[jyothsna pb]

does the force exerted by the robotic arm lead to a change in velocity? so won't there b a change in KE

 

[sponsoredwalk]

Hi thanks for the informative answer.

Well yeah, while the robotic arm exerts a force on the asteroid it will accelerate the asteroid forward for say 5 seconds, initially the asteroid has velocity $$v_1$$ and then after the robotic arm let's go 5 seconds later the asteroid moves forwards faster with velocity $$v_2$$.

My second part was unclear, sorry about that. I've got it now I was just confused for one second after reading a quack paper on kinetic energy.

 

[rdl]

I can provide a response to your questions about the kinetic energy of an asteroid moving in space.

1. Yes, the asteroid will still have the same kinetic energy as it did when it was released from the robotic arm, even if an hour has passed. According to Newton's First Law of Motion, an object in motion will remain in motion unless acted upon by an external force. In this scenario, since there is no external force acting on the asteroid, its velocity will remain constant and therefore its kinetic energy will also remain constant.

2. The kinetic energy of an object is only affected by external forces acting on it. In this case, the ship exerted a force on the asteroid for a few seconds, which increased its kinetic energy. However, once the force is removed, the kinetic energy will remain constant. The ship itself will also have kinetic energy as it is moving, but this is a separate calculation from the kinetic energy of the asteroid.

It is important to note that while the asteroid may not have any external forces acting on it, it still has internal energy due to its motion. This internal energy is known as thermal energy, which is a form of kinetic energy at the molecular level. So even though the asteroid may not have any external forces acting on it, it still has kinetic energy at the molecular level.

In summary, the kinetic energy of an object is only affected by external forces acting on it and will remain constant if there are no external forces present. I hope this helps clarify any confusion about kinetic energy in this scenario.