G force question (1 Viewer)

[cutemouse]

Hi all,

I have a question - "A rocket is accelerating from between Mars and Jupiter at 26.95ms^-2. Calculate g-force on a 60kg astronaut.

I'm really stuck on this, please show me how you got the the answer.

Thanks,

Jason

 

[adnan91]

Hi all,

I have a question - "A rocket is accelerating from between Mars and Jupiter at 26.95ms^-2. Calculate g-force on a 60kg astronaut.

I'm really stuck on this, please show me how you got the the answer.

Thanks,

Jason

Do u have the answers? my answer is 2.75

 

[cutemouse]

Yep, 2.75 is correct according to the back of the book. Can you please tell me how you got to that?

Thanks,

Jason

 

[tommykins]

26.95/9.8 = 2.75

 

[cutemouse]

Oh okay. Thank you

So as g forces = apparant weight/true weight, is the 'true weight' always the weight experienced on Earth?

 

[tommykins]

yes.

 

[henry08]

I got 3.75.

 

[tommykins]

I got 3.75.

I've always had an issue with that, do you add 9.8 to compensate?

I don't know, some questions you add an extra one, some you don't (like in this one where he says the textbook claims it is 2.75)

 

[Pwnage101]

I've always had an issue with that, do you add 9.8 to compensate?

I don't know, some questions you add an extra one, some you don't (like in this one where he says the textbook claims it is 2.75)

i think we do add 9.8, heres my reasoning:

we define 1g to be normal, true weight on surface of eart, ie currently u and i are feeling 1g - ie our acceleration is (0+9.8)/9.8 = 9.8 = 1g

we feel 0g when we are in free fall, correct so we are accelerating downwrads at 9.8 to do this, ie (-9.8 +9.8)/9.8 = 0g

in order to get negative g's WE MUST SUPPLYA CCELERATION SO THAT WE FALL WITH AN ACCELERATION THAT EXCEEDS NORMAL FREE FALL

we feel 2 g's when accelerating away from earth at 9.8 - that is our acceleration = (9.8+9.8)/9.8 = 2g

in all these cases u must add 9.8

its a bit confusing but makes sense in a way, lets change the Q above to someone escaping from earth - it says they are accelerating with that value, so uve got to take into account that by providing no accleration against gravity, we are in free fall

in order to stay where we are in the earths atmosphere, we must counteract it & supply 9.8 acceleration up - then we wont move (the whole the ground exerts a force on me so i stay where i am thing that confused us in year 9)

now in order to accelerate 26.95 m/s^2 as the Q says, i think they mean net acceleration is 26.95, so IN ACTUAL FACT they would have to supply an acceleration of 26.95+9.8 = 36.75 in order to gain a neta cceleration of 26.95,, as 9.8 goes towards counteracting acceleration due to gravity down

so i dont think the book has taken into account that the roket is being pulld down by acceleration due to gravity, so when it says "A rocket is accelerating from between Mars and Jupiter at 26.95ms-2. Calculate g-force on a 60kg astronaut" i think they should say "A rocket is accelerating in space at 26.95ms-2, where the effect of planets' gravity is negligible. Calculate g-force on a 60kg astronaut"

plus, we dont even know the acceleration due to gravity at mars....so i rekon the Q is a bit simple in its idea

ive rambled, but anyone agree/discagree with me???

 

[henry08]

G force = (g + a)/9.8

= 3.75

 

[syriangabsta]

i think we do add 9.8, heres my reasoning:

we define 1g to be normal, true weight on surface of eart, ie currently u and i are feeling 1g - ie our acceleration is (0+9.8)/9.8 = 9.8 = 1g

we feel 0g when we are in free fall, correct so we are accelerating downwrads at 9.8 to do this, ie (-9.8 +9.8)/9.8 = 0g

in order to get negative g's WE MUST SUPPLYA CCELERATION SO THAT WE FALL WITH AN ACCELERATION THAT EXCEEDS NORMAL FREE FALL

we feel 2 g's when accelerating away from earth at 9.8 - that is our acceleration = (9.8+9.8)/9.8 = 2g

in all these cases u must add 9.8

its a bit confusing but makes sense in a way, lets change the Q above to someone escaping from earth - it says they are accelerating with that value, so uve got to take into account that by providing no accleration against gravity, we are in free fall

in order to stay where we are in the earths atmosphere, we must counteract it & supply 9.8 acceleration up - then we wont move (the whole the ground exerts a force on me so i stay where i am thing that confused us in year 9)

now in order to accelerate 26.95 m/s^2 as the Q says, i think they mean net acceleration is 26.95, so IN ACTUAL FACT they would have to supply an acceleration of 26.95+9.8 = 36.75 in order to gain a neta cceleration of 26.95,, as 9.8 goes towards counteracting acceleration due to gravity down

so i dont think the book has taken into account that the roket is being pulld down by acceleration due to gravity, so when it says "A rocket is accelerating from between Mars and Jupiter at 26.95ms-2. Calculate g-force on a 60kg astronaut" i think they should say "A rocket is accelerating in space at 26.95ms-2, where the effect of planets' gravity is negligible. Calculate g-force on a 60kg astronaut"

plus, we dont even know the acceleration due to gravity at mars....so i rekon the Q is a bit simple in its idea

ive rambled, but anyone agree/discagree with me???

I agree..
its quite stupid how a textbook claims otherwise...what if lets say the markers in our hsc think the same way a textbook does, and put the answer down as 2.75...

then all those who are okay at physics, put 2.75 and get it right...and those who are leet at physics put 3.75 and get it wrong....scary thought @@

 

[Continuum]

I think it should be 2.75.

G-force is a measure of apparent weight over true weight. The apparent weight that the astronaut experiences would be the force due to acceleration of the rocket and acceleration due to gravity. I don't get why people automatically put 9.8 as acceleration due to gravity for this question, since it isn't from Earth but Mars or Jupiter. As the question doesn't specify which one, I reckon it'd be safe to assume it isn't a consideration (I agree that it's a bad question). Thus, all we have is the simple 26.95/9.8, which is 2.75.

 

[dolbinau]

F=MA

F=(60)(26.95) =1617 N

F=(60)(9.8) = 588 N

(1617/588)= 2.75

Of course this is pointless as you can cancel out the mass and just do 26.95/9.8 but still, I think it's 2.75 because the apparent weight is 2.75 greater than his actual weight (measured on earth as 588N).

Now, if he was accelerating on Earth then you'd need to add 9.8 for weightforce but as it isn't you don't have to IMO.

 

[adnan91]

geez u talk too much. Ok sometimes u use g+a/g to calculate gforce and sometimes u use apparent weight/ real weight. From the question they give u his MASS so obviously they want u to use app. wgt/real wght.

 

[Continuum]

geez u talk too much. Ok sometimes u use g+a/g to calculate gforce and sometimes u use apparent weight/ real weight. From the question they give u his MASS so obviously they want u to use app. wgt/real wght.

It's better to work it out by actually understanding the question... What you're referring to is the same thing you know, so that reasoning doesn't really work. :mad1:

G-force=apparent weight/real weight=(mg+ma)/mg=(g+a)/g

 

[adnan91]

It's better to work it out by actually understanding the question... What you're referring to is the same thing you know, so that reasoning doesn't really work. :mad1:

G-force=apparent weight/real weight=(mg+ma)/mg=(g+a)/g

I was trying to help in regards to which formula u use for different questions

 

[henry08]

So is it 2.75 or 3.75?

 

[dolbinau]

The book says it was 2.75, and I personally think it is 2.75.

 

[ratcher0071]

g-force = F_{apparent weight} / F_{true weight}


apparent weight: F_{apparent weight} = ma
F_{apparent weight} = 60kg x 26.95m/s²
F_{apparent weight} =1 617 Newtons

true weight (weight on Earth): F_{true weight}=ma
F_{true weight} = 60kg x 9.8m/s²
F_{true weight}= 588 Newtons

g-force = 1 617/588
g-force= 2.75

 

[samwell]

Hi all,

I have a question - "A rocket is accelerating from between Mars and Jupiter at 26.95ms^-2. Calculate g-force on a 60kg astronaut.

I'm really stuck on this, please show me how you got the the answer.

Thanks,

Jason

i did this question from dt point. since g at a point is give by {g=GM/r^2) and an object is btn mars and jupiters its g is close to zero but g forces are a ratio of apparent weight/ real weight thus g+a/9.8= 26.95+0/9.8