Questions from CSSA (1 Viewer)

[Rahul]

Question 18
(a) the gravitational potential energy at a point is defined as the work done to move an object from a very large distance to that point in the gravitational field.
Apply this statement with reference to a meteor that is moving towards Earth from a long distance away.

Question 20
(c) Outline where and how a transformer similar to the one above[which was a step down transformer] could be used to asist in the transmission of high voltages(approx 35KV) to home requiring only a 240V supply.

What would be the answers?

I want to compare it with mine so i might get some more marks

 

[Ragerunner]

18) i stated the formula work = force x distance

then explained that work is required to move a object from a point of infinity to a point in space. then with reference to the meteor, i restated that bit using the meteor as an example. had to fill up the rest of the lines

20)substations. at the outskirts of the city, substations are used to step down the voltage to 240 for home use. how it does it is it uses a secondary coil with less turns in it.

 

[Ragerunner]

i also got a question. For the one about safe re-entry where they gave us a picture and says to name these safety features.

our teacher told us sacraficial parts which get vaporised after they absorb the heat is entirely wrong. He understands that all textbooks mention something about sacraficial parts but he doesn't believe it and says ALL the textbooks are WRONG and HE is RIGHT because he read the NASA website. He even said that that answer i put was in the marking guidelines but he doesn't care because its wrong

isn't that unfair?

 

[underthesun]

talk about stupid teachers..

btw, for that gravitational potential energy, someone used that F = -Gm1m2/r formula.

The thing is, he put the r value as the distance from the meteor to the surface, not the earth radius. And that's the answer from the CSSA paper, so he got 1 mark.

See how stupid CSSA people are?

How I love CSSA bashing..

Even worse are the teachers who just blindly and zealously defends CSSA's answers, even though it's wrong. Stupid teachers. Why are they even teaching physics?

ah.. i feel better now

 

[Ragerunner]

actually i think the CSSA one was wrong.

i also did the same thing the guy did

you must use the radius as (1000m + earth radius)

can't believe i forgot that

 

[Rahul]

Originally posted by Ragerunner
our teacher told us sacraficial parts which get vaporised after they absorb the heat is entirely wrong. He understands that all textbooks mention something about sacraficial parts but he doesn't believe it and says ALL the textbooks are WRONG and HE is RIGHT because he read the NASA website. He even said that that answer i put was in the marking guidelines but he doesn't care because its wrong

isn't that unfair?

thats bullshit! i think ur talking about 'ablative' materials. i got marks for that.

want a stupid teacher, for q20 (c), he didnt read all my answer! i had to get him to add a mark to my tally.

 

[Ragerunner]

yes but i didn't use the word "Ablative"

i used sacraficial. which i learned from "Surfing Physics"

nooooooo i had 2 marks first then he changed it to 1. fagx100000000000000000000

 

[underthesun]

What was this "come" writing? Is blunt nose the proper word?

 

[Ragerunner]

blunt "cone" he wanted

he said he was -generous- and gave me the mark.

 

[jims]

for the one about substations, the cssa answer required you to actually calculate the number of turns in the primary and secondary coil, which is pretty stupid considering the question says outline.

 

[Rahul]

yep spot on there jims....you had to calculate the ratio for a mark.

what to take out of the question, if numerical data is given, then u must use that in ur answer

 

[ND]

Originally posted by Ragerunner
actually i think the CSSA one was wrong.

i also did the same thing the guy did

you must use the radius as (1000m + earth radius)

can't believe i forgot that

But nowhere in the datasheet was the value for the radius of the earth. There is also a formula which allows you to calculate it within short distances, but that wasn't on the datasheet either. I wrote "Not enough info given to answer question".

 

[Rahul]

Originally posted by ND
But nowhere in the datasheet was the value for the radius of the earth. There is also a formula which allows you to calculate it within short distances, but that wasn't on the datasheet either. I wrote "Not enough info given to answer question".

are you sure u need to include the radius and 1000m?
jacaranda says to put d (or r) as the distance separating the masses.

 

[ND]

I think it's supposed to be from the centre of gravity.

Did anyone see the CSSA solutions? There were so many wrong ones. They even had very simple ones wrong, like that mulityple choice involving the graphs of current vs rotation of a generator; the answer had the graph of an AC generator, even though the generator in question had a split ring commutator.

 

[Rahul]

for that question, note that the graph was current vs time, not emf(voltage) verses time.

in the case of emf vs time, it would have been part d, the straight line.

 

[Ragerunner]

for that gravitatiional potential maths question teacher told us not a single person got it right in my school. i still don't know how to work it out if its not in the data sheet

 

[ND]

for that gravitatiional potential maths question teacher told us not a single person got it right in my school. i still don't know how to work it out if its not in the data sheet

*flips back through excel physics*

The GPE when the object of mass m is a short distance h from the earth is given by GPE = mgh. Either that or know the radius of the earth.

But i don't think that was a legit question without giving either that equation of the radius of earth.

are you sure u need to include the radius and 1000m?
jacaranda says to put d (or r) as the distance separating the masses.

In the excel book is says "distance r from centre of the earth (or other planet)".

 

[underthesun]

I think it is also the same with macmillan physics, that the distance is from the centre of the earth.

Otherwise, you'd have infinite gravitational potential energy (woot) as you're 0 metres above the earth surface.

 

[Rahul]

well then how are we sposed to calculate that question? they cant get us to remember the radius of earth surely....damn cssa.

 

[Ragerunner]

our teacher came up with a numerical answer. i bet he just looked up the radius of the earth and says too bad suckers you all got it wrong :/