G forces? (1 Viewer)

[aero135]

Is Dot point by Shadwick B wrong on these questions?

2.6.2 - A rocket i accelerating from the launch pad at 26.95 ms-2

(a) Calculate the g - force on a 60kg astronaut

answer is 3.75

(b) Predict the g - force acting on a 80kg astronaut

answer is 3.75

2.6.3

A rocket is accelerating from between Mars and Jupiter at 26.95 ms-2. Calculate the g - force on a 60kg astronaut.

answer is 2.75

can you please show working so i can understand how u derived the answer

cheers!

 

[rheyn]

Is Dot point by Shadwick B wrong on these questions?

2.6.2 - A rocket i accelerating from the launch pad at 26.95 ms-2

(a) Calculate the g - force on a 60kg astronaut

answer is 3.75

(b) Predict the g - force acting on a 80kg astronaut

answer is 3.75

For this question, the book's answers are right

Working for both a) and b):

the rocket is on earth therefore g= 9.8 m/s/s

acceleration is 26.95 m/s/s

Formula: g force = apparent weight/ true weight
= (mg+ma)/mg
Therefore g force = (g+a)/g

sub in the values => (9.8 + 26.95)/9.8 = g force
3.75 = g force


N.B. for this question the data about the astroaut being 60/80 kilograms is irrelevant

 

[M@ster P]

That's alot of units you doing rheyn

 

[aero135]

Rheyn mate what about this question?

2.6.3

A rocket is accelerating from between Mars and Jupiter at 26.95 ms-2. Calculate the g - force on a 60kg astronaut.

answer is 2.75

u didnt answer it! LOL

 

[imoO]

g-force = 1+ a/g

= 1 + 26.95/9.8
= 1.27 (approx.)

Note - The weight is completely irrelevant to what you are calculating. In reguards to my formula

(ma+mg)/mg, can be written as mg/mg + ma/mg
mg/mg is 1

ma/mg can be simplified by canceling out the 'm'

therefore g-force = 1+ a/g

 

[rheyn]

g-force = 1+ a/g

= 1 + 26.95/9.8
= 1.27 (approx.)

I don't think that calculation is quite right because 1+26.95/9.8=1+2.75=3.75
But the algebra is fine.

Rheyn mate what about this question?

2.6.3

A rocket is accelerating from between Mars and Jupiter at 26.95 ms-2. Calculate the g - force on a 60kg astronaut.

answer is 2.75

u didnt answer it! LOL

Aero with the information that has been presented, I'm not too sure about how to go about it, because the space rocket is no longer on earth, therefore g is no longer 9.8.

Usually that wouldn't be a problem because we could just calculate g by working out the net gravitational force (exerted by Mars and Jupiter) acting upon the space rocket using the law of universal gravitation. However we are not provided with the mass of Mars nor Jupiter, nor are we provided with the distance from the space rocket to mars or jupiter.

Are you sure there is no additonal data?

 

[aero135]

no additional info, but now im confused on which method to use

isnt it acceleration + 9.8 over 9.8?

 

[rheyn]

no additional info, but now im confused on which method to use

isnt it acceleration + 9.8 over 9.8?

What method were you planning on using?

you can't use 9.8 anymore because that is acceleration due to gravity on earth, but now the rocket is in space so the accerelation due to gravity that it experiences is from Jupiter and Mars.

I was planning to work out g using the Law of Universal Gravitation then simply plug it into: 1+26.95/g= g force

 

[rheyn]

I am such an idiot- I know how to do it now.

As the rocket is accelerating from Mars, the gravity of Earth is ignored, so the g of Earth is zero. But the g force is defined as: (mg + ma) / mg , that means the force acting on astronaut is compared with the gravity of Earth acting on the astronaut. For this question, the true weight of astronaut on Earth is mg, the force experienced on rocket at that moment is ma; thus, the g-force should be

g-force = ma / mg = 26.95 / 9.8 = 2.75 ​

For Mars’ gravity, due to the rocket is flying, just passing by the Mars, not close to the Mars and not affected by Mars because the travelling direction of the rocket is perpendicular the distance between the rocket and the centre of Mars; therefore the Mars’ gravity is still ignored.