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.Gabriele Pinna said: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
haruspex said: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.
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.haruspex said: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.
Please read https://www.physicsforums.com/threads/guidelines-for-students-and-helpers.686781/GrimReaper said: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.
Thank you very much.haruspex said:
The reference to force in the question statement is clearly an error. It should have said energy.mjc123 said:Why is there no answer to this question? (Apart from the obvious fact that the question asks about force and gives answers in energy...)
oh sorry, actually its energy. I mistakenly typed force.haruspex said:The reference to force in the question statement is clearly an error. It should have said energy.
The answer is given in post #2.
KE+PE, or kinetic energy plus potential energy, is a measure of the total energy of a rocket when its speed is less than escape velocity. It is the sum of the rocket's kinetic energy, which is the energy it possesses due to its motion, and its potential energy, which is the energy it possesses due to its position in a gravitational field.
When a rocket's speed is less than escape velocity, its KE+PE is affected by the rocket's mass, the planet's gravitational pull, and the rocket's height above the planet's surface. The rocket's KE+PE will be at its maximum when it is at the planet's surface and decreases as it gains altitude.
When a rocket's speed is increased beyond escape velocity, its KE+PE will increase as well. However, the rocket's kinetic energy will be greater than its potential energy, and the total energy will be positive. This means that the rocket has enough energy to escape the planet's gravitational pull and continue into space.
The concept of KE+PE is important in rocket launches because it helps determine the amount of energy needed for a rocket to escape the planet's gravitational pull. By calculating the KE+PE at different stages of the launch, scientists and engineers can determine the ideal trajectory and speed for the rocket to reach its desired destination.
Yes, a rocket with a speed less than escape velocity can still reach space. As long as the rocket has enough energy to overcome the planet's gravitational pull, it can continue to gain altitude and eventually reach space. However, it may require more fuel and a longer trajectory compared to a rocket with a speed greater than escape velocity.