Space Help 2 (1 Viewer)

[mrzeidan1]

Hey..

Imagine that you were to travel in a spacecraft of mass 10,000kg from the Earth to the Moon. After liftoff, you intend to orbit the Earth at an altitude of 40,000km and then proceed to the moon.

Have to investigate the force and energy at different points on the journey, and am confused as hell... I keep getting weird answers

Help thanks

 

[twilight1412]

well in terms of energy and force

energy: potenial energy
force: gravitational force

take points:

on surface of earth
in orbit at 40,000km
on moon

 

[alcalder]

The forces on the rocket on Earth:

Stationary - Gravity weight force and normal force of Earth on rocket. Thus, the rocket is not moving anywhere. GPE = minimum, KE = 0

Taking off - Gravity Force down, Drag down, thrust up, Wing lift. For the rocket to lift up it must have a total force upwards, thus Thrust + Lift > Gravity+Drag. GPE increasing, KE increasing - the Total Energy = initial KE + GPE is kept constant throughout rocket motion.

In Orbit - Gravity down due to Earth keeps the rocket in orbit. GPE given by equation, KE up and down is zero since it is in orbit, but it does have KE in tangential orbit.

On way to moon - at some point the rocket may/may not exit the Earth's gravitational field, will enter the Moon's gravitational field. Thus forces will be gravity of moon, gravity of earth, thrust (no drag or lift since no atmosphere). GPE will continue to increase from Earth and will decrease towards the moon, KE is what it is.

I think that about covers it all, but you may think of something else.

Hope it helps.