need help (1 Viewer)

[kcuf]

hi i've got some qns that are confusing me

1. there was once a proposal to launch satelites directly into a circular orbit that's a constant distance from the earth, using a giant world war 1 cannon. assuming that the cannon could give the satelite a high enough velocity, explain why this proposal would not work.

2. if there is a question asking me to calculate the orbital velocity, do i use the formula "v=2pir/t" or "v=root of GM/r". becoz the 2nd one didnt specify the planet. or can i use both?

3. see attachment


Thanks in advance

 

[zingerburger]

1. Not sure about this one.

2. You could use either, depending on the information given by the question. If you used "v=2*pi*r/t" you would need the radius of the orbit (i.e. the radius of the planet and the distance of the satellite from the planet's surface) and the orbital period (i.e. the time it takes the satellite to go around the planet once.

If you used "v=root of GM/r" then you would need the orbital radius again, and the mass of the planet. "G" (6.67^-11) is the Universal Gravitational Constant in case you don't know, but should be on the data sheet they give you.

3. Since it's a "Compare" question and is only worth 2 marks, all you need to do is provide 1 similarity and 1 difference, preferably in the form of a table.
E.g. They are similar because both the observers would see the light beams hitting their targets. But they are different because the observer off the train would see one target get struck before the other did.

 

[morganforrest]

For Question 1 there are a fair few answers you could give. A couple of potential responses are...g forces would tear the satellite apart as the instantaneous velocity jump would be too great, 8 km/s is a lot to ask for from a cannon (thats the minimal specific velocity required to put something into a circular orbit around earth),

These are the only things I can really think of...it seems like a pretty obscure sort of question. I'd be interested to hear what your teacher thinks is the right answer.

 

[xiao1985]

for q 1, you can also look at the fact that when it is at the right altitude, it need to keep a tangential velocity, which it is unable to maintain (unless you elevate the cannon to the desired altitude)