• Livestream AMA: Join SDN as we welcome Dr. John Ligon, a Pediatric Oncologist with the National Cancer Institute on May 11th at 8:00 PM Eastern. Register now!


There was a physics uworld question which proposed that an object is launched away from a planet with no atmosphere, and it said to pick the choice that describes the changes that occur as the object moves away from the planet's surface.

The options included:
A. The object mass is dissipated as heat.
B. PE is converted to KE
C. KE is converted to PE
D. Total mechanical energy is not conserved.

I picked B, but the answer was C. I was confused, because the question stated that the planet had no atmosphere, so wouldn't there be no gravitational force? Without a gravitational force, how do you have PE as the object moves away from the planet surface? Wouldn't the object launch with an initial speed, and then just continue with that same speed since there is no gravitational force opposing it?


I think the no atmosphere phrase was to note there was no friction of passing through air. There can absolutely be a gravitational pull without atmosphere

Given that, as the object moves away it turns KE into PE as it simultaneously both slows down and has farther to fall when it returns to the ground
About the Ads
This thread is more than 1 year old.

Your message may be considered spam for the following reasons:

  1. Your new thread title is very short, and likely is unhelpful.
  2. Your reply is very short and likely does not add anything to the thread.
  3. Your reply is very long and likely does not add anything to the thread.
  4. It is very likely that it does not need any further discussion and thus bumping it serves no purpose.
  5. Your message is mostly quotes or spoilers.
  6. Your reply has occurred very quickly after a previous reply and likely does not add anything to the thread.
  7. This thread is locked.