# Entropy falling objects

• kimpantip

#### kimpantip

Dear sir,

Hi, Everyone. I have a question about entropy. If the object falls without air resistant (vacuum system) , Is entropy changed? If ΔS=0, it means reversible, is it possible that the object can go back to the original height? I know that it is impossible but can we explain that ΔS >0.
Within the condition as following:
*** Focus on within the space (free falling under gravity)

Thank you very much
Sincerely,

If the object falls without air resistant (vacuum system) , Is entropy changed? If ΔS=0, it means reversible, is it possible that the object can go back to the original height?
What do you think?

I know that it is impossible
Why? Assuming there are no other mechanisms where energy gets lost (inelastic collisions for example).

What do you think?

Why? Assuming there are no other mechanisms where energy gets lost (inelastic collisions for example).

The thing that I wonder is how can entropy increase while the object is falling in spite of no air resistant and no collision on the ground.

That's my question: why do you think it would increase?

why do you think it would increase?

ifΔs=0 it reversible, object is able to rise! so i think that Δs>0

ifΔs=0 it reversible, object is able to rise!
Sure it is, and it will do so after a perfect elastic collision (or a frictionless U-shaped ramp).