Escape Velocity Question!!! (1 Viewer)

[superSAIyan2]

Hey guys,

Can someone please clarify this for me : Escape velocity doesnt mean a satellite is in circular orbit right? It means it has completely escaped a planets gravitational field?

Also I have a question where it asks you to calculate the Earth's escape velocity and I got 11200m/s. Then part b) says why is this value more than the actual velocity of space probes that leave the Earths grav field.

Is it because the value calculated is the escape velocity at the Earths surface. And as space probes actually leave the Earths grav field at a much larger distance from its centre they have a smaller escape velocity. This is because escape velocity is inversely proportional to the distance (or square root of distance to be specific)

 

[RealiseNothing]

To be more correct, escape velocity is the minimum velocity required for an object to leave the planet's gravitational field, and once left it will cease motion.

 

[DamTameNaken]

Can someone please clarify this for me : Escape velocity doesnt mean a satellite is in circular orbit right? It means it has completely escaped a planets gravitational field?

Second one. Escape velocity means the object has escaped the planets orbit entirely. Be careful not to say it has escaped the gravitational field as gravitational fields have an infinite distance.

part b) says why is this value more than the actual velocity of space probes that leave the Earths grav field.

Escape velocity was originally devised by Newton as a thought experiment were a cannonball was fired out of a cannon. the 11200m/s refers to the initial speed of the cannonball were there is no other force to act on the cannonball apart from gravity. The reason this speed doesn't apply for space shuttles is because they have a constant force accelerating them upward from the thrusters burning up fuel, this means they don't need a super fast initial speed because they have upward acceleration whereas the cannonball has downward acceleration due to gravity.

 

[RealiseNothing]

Second one. Escape velocity means the object has escaped the planets orbit entirely. Be careful not to say it has escaped the gravitational field as gravitational fields have an infinite distance.

No it is definately the minimum velocity required to escape the Earth's gravitational field, even if that is at an infinite distance away.

 

[DamTameNaken]

No it is definately the minimum velocity required to escape the Earth's gravitational field, even if that is at an infinite distance away.

Just re-read the section in the textbook and you're definitely right. Good pickup.

 

[planino]

circul

square

.

 

[someth1ng]

In reality, escape velocity would be the minimum velocity required so that the object will always move away from the planet (it will stop moving away when it reaches infinity).

It's not the way you put it but that's how you can see it.

 

[Fizzy_Cyst]

dont use the word 'object', use the word 'projectile', one of the key things is that the 'object' must not be powered.

 

[someth1ng]

dont use the word 'object', use the word 'projectile', one of the key things is that the 'object' must not be powered.

Yes, projectile is a better word and the second part is also true - it is the initial velocity such that no further propulsion is required.

 

[abbeyroad]

play orbiter ok

http://orbit.medphys.ucl.ac.uk/

 

[romesh]

Actually I think that Kerbal Space Program would be a great teaching aid for high school space/orbital physics, because by dropping some of the realism of Orbiter it really gets to the important concepts

 

[Fizzy_Cyst]

Actually I think that Kerbal Space Program would be a great teaching aid for high school space/orbital physics, because by dropping some of the realism of Orbiter it really gets to the important concepts

I use KSP some students really get into it! Takes quite some time to master. Took me weeks to even get to the Mun, let alone back.