KE+PE when a rocket's speed is less than escape velocity?

1. Jul 18, 2017

GrimReaper

Hey people, I just want to ask that what will happen to the total mechanical force of the rocket if its speed is less than escape velocity?
a. KE+PE=0
b. KE+PE>0
c. KE+PE<0
d. Depends upon initial speed of the rocket
Pick one. And Why??

2. Jul 18, 2017

Gabriele Pinna

I guess C because at infinity we will have PE=0 and KE> 0 or equal to zero. As the rocket has not the tendency to move to infinity we conclude that
PE+KE <0

3. Jul 18, 2017

haruspex

I appreciate that it was a bit tricky with this one, but the rule on homework forums is to give hints and point out errors, not provide complete solutions.
Correspondingly, @GrimReaper should have used the homework template and shown some attempt before meriting any help.

4. Jul 18, 2017

GrimReaper

I'm sorry if it was a mistake. And I'm totally new to this so I actually don't know how to use this. Thank you for the directions @haruspex.

5. Jul 18, 2017

haruspex

6. Jul 18, 2017

GrimReaper

Thank you very much.

7. Jul 18, 2017

mjc123

Why is there no answer to this question? (Apart from the obvious fact that the question asks about force and gives answers in energy...)

8. Jul 18, 2017

haruspex

The reference to force in the question statement is clearly an error. It should have said energy.
The answer is given in post #2.

9. Jul 19, 2017

GrimReaper

oh sorry, actually its energy. I mistakenly typed force.