Projectile Energy Multiple Choice (1 Viewer)

[Jase]

Yes that's what i was thinking, convo of energy states that the TOTAL energy of a system is constant.. but this question sucks.. like seriously, the actual states of PE and KE change, as it works in respect to the earth's gravitational field.

Anyway, this is from the STANNSW trials 2003.. i can honestly say, it's a hard paper.
It's not so much controversy, it's just plain hard.
I really hope we don't get this kind of thing tomorow.

 

[JayWalker]

energy should be constant- conservation of energy. So energy can't vary. The type of energy can, but not the amount of energy.

No because the energy gets transfered from the bullet to something else for example sound.. that is not related to the bullet

 

[scorpi0n]

A bullet is fired into the air.
If all friction and resistance is negligible, which of the following statements are true:

A) Energy of the bullet and acceleration remain constant
B) Energy varies and acceleration remains constant
C) Energy constant while acceleration varies
D) Evergy and acceleration both vary.


Dosn't the projectile gain potential energy as it moves up, and lose KE as it goes down, so its energy varies?

terrible question. acceleration is constant at -9.8ms^-2...
energy is also constant...but it "varies" in terms of states as you said jase, ie KE to GPH, but in terms of total energy it remains constant. hence the dodgy-ness of the question, not very specific. i'd still put a), i'd assume its talking about the energy of the system. lets hope we dont get anything this ambiguous tomorrow...

 

[Xayma]

Anyway if you are going to be so trivial as to take the heating of the bullet due to the explosive force you must take into account that as it rises the gravity changes (very slightly though)

 

[Jezzabelle]

yeh.. like at the poles,the equator and high places like everest.... pretty negliable really

 

[tennille]

People should take into account that this is only a multiple choice question. It doesn't require over- analysing. It's worth one mark.

 

[onepac]

energy is constant, like Xayma said because of the Law of Conservation of Energy, however acceleration is not constant as the projectile moves away from Earth and the acceleration due to gravity is slightly less than 9.8 at the peak.