FREE Physics Tutoring (jks just free help) Thread (1 Viewer)

[eyeseeyou]

1. Discuss how the rotational motion of the Earth can be used to improve fuel efficiency for rocket launches. (3 marks)
2. Evaluate the use of the term “g-force” in explaining the forces acting on an astronaut during the launch of a rocket. (4 marks)

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How do you write a response which gets you full marks

 

[pikachu975]

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How do you write a response which gets you full marks

aka write my physics notes for those syllabus dot points

 

[eyeseeyou]

Ok got a question

Is there much GPE when you are in water, if so why/why not?

 

[kashkow]

lel

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How do you write a response which gets you full marks

This would be my approach. I'm not 100% sure this would gain full marks. (If you have them I'd look at the marking guidelines or marking notes for further advice if available)

For the first one I'd try identify 1-2 relevant points and discuss them. I'd probably go with 1. Launching east to take advantage of Earth's rotation and 2. launch windows (though this may be considered orbital, not rotational so may talk less about this) as these both increase relative velocity to the sun. Then I'd talk about how fuel is saved than if a direct route was taken in a launch.

Second one I'm not sure what kinda question this is and whether this is part of the syllabus. Like it's asking to talk about whether the term "g-force" is suitable? I'm guessing it's more talking about how "g-forces" work more and then relating it to the name or something in which case I'd explain what g-force is and relate it to it's name (how it involves (g+a)/g).

 

[jazz519]

Part 1. I would do the same as above for saying launching to the east in the same direction as the Earth etc. but I would add u locate the launch site for the rocket closest to the equator, because there is the greatest rotational motion there because as velocity = distance /time, because a place at equator has to cover more distance because the circumference of earth is biggest there in the rotation in the same time (24 hours), the velocity has to be greater. Then link this to making it more economical because less fuel is needed and a greater velocity is obtained.

Part 2. Yeah the q is weird saying evaluate, normally it's an explain or describe, so if it was describe I would do this for the 4 marks. Define what g-force is: g - force is a convenient way to express the contact force on astronaut in multiples of what they would normally experience on earth (gforce = 1 + a/g). Then discuss like the different stages. Prior to launch: the rocket is stationary on the launchpad therefore there is no acceleration and thus a g force of 1 is experience. During lift-off: remains constant at 1 g force, until the thrust of the rocket overcomes the weight force, and at this point the g force experienced is slightly greater than one. From here on: as fuel is expended the mass of the rocket decreases, and as a = T-mg/m by newtons 2nd law, as acceleration is inversely proportional to mass of rocket, the acceleration of the rocket increases and thus gforce also increases. However, in multi stage rockets, when all fuel is expended in one rocket stage the rocket momentarily is in free fall and thus at this point a g force of 0 is experience. Also, at peaks of the g force a human can safely withstand engines are momentarily shut off to ensure safety of astronauts.

 

[kashkow]

Ok got a question

Is there much GPE when you are in water, if so why/why not?

Do you need help with this? Or are you testing my knowledge in these questions? It's fine if it's the second option but I'd probably prefer that a) you don't spam this thread and b) you try keep it relevant (ie. in syllabus) that way it's actually useful for me too. Not saying you are spamming right now but I don't think this question is part of the syllabus.

In terms of an answer, I think there's too many factors to consider such as buoyancy and density. Do you sink or float and to what degree? Thinking of it in broad terms if you naturally sink but are being held up then there is some gravitational potential energy: because there is energy that isn't kinetic but it has the potential to sink. If you naturally float then you don't have any GPE as any potential energy from being held underwater would be from an external force and not gravity. ie. the gravity is not giving it potential energy to float. lelelel this is me guessing, I don't really know and google is probably your friend here.

 

[kashkow]

Part 1. I would do the same as above for saying launching to the east in the same direction as the Earth etc. but I would add u locate the launch site for the rocket closest to the equator, because there is the greatest rotational motion there because as velocity = distance /time, because a place at equator has to cover more distance because the circumference of earth is biggest there in the rotation in the same time (24 hours), the velocity has to be greater. Then link this to making it more economical because less fuel is needed and a greater velocity is obtained.

Oh yeah forgot about that.