# answer to Q4 (multiple choice) (1 Viewer)

#### rent

##### New Member
well obviously you don't do 4U maths, spice girl.

i'm saying since "a" is derived from a "weight" force, it has to be either upwards or downwards in direction.

#### Yeebies

##### New Member
its when the rollercoaster is travelling upwards. g-forces are negative when something is 'falling', and positive when 'pulling out' - as says excel.

so... if max g force is when g>1, then the only time the g forces are positive is when your 'pulling out'

#### rent

##### New Member
when a rollercoaster is going up - g force >1, when it is going down, g force <1. That's what jacaranda says.

but g forces are always directed upwards for rockets.

#### Minai

##### Alumni
Originally posted by rent
well obviously you don't do 4U maths, spice girl.
hahahaha

#### Ronnie

##### Member
Blooody Hell

think of when you're in a roller coaster!

when do you feel as if you hit a brick wall? thats when G forces are at max!

I'm not sure as to what letter it is, but it is at the bottom because you fall down at a fast rate and then it abruptly stops and starts going up!

when you're climbing up you feel jackshit because it's climbing up at a slow rate

#### BlackJack

##### Vertigo!
Originally posted by rent
well obviously you don't do 4U maths, spice girl.
:rofl:*composes himelf, and motions 'sorry' *

...she does do 4unit maths...

#### spice girl

##### magic mirror
Think about going up or down a lift. The time when you feel the "heaviest" is when you slow down as you reach the ground floor or when you initially speed up when you go upwards. If you connect going down and going up as one event, the middle of your max g is at ground floor (parallel to Q)

#### McLake

##### The Perfect Nerd
When is max "a" in SHM? When you have a directional change ...

PS: I know this isn't SHM but the same principle applies ...

#### Mr Chicken

##### New Member
G forces are just a way of measuring acceleration!
the only place on a roller coaster than the g forces could possibly be more than 1 is at the turning points on the loops (unless it's a rocket powered roller coaster..?!)
so stop trying to argue that C is correct, it's really not!

#### Ace-Pilot

##### Member
God damn some one call board of srudies and solve this already !!

#### bigsexy

##### New Member
the answer is B. my uncle is a science teacher and he said it is B
C would have negative g-forces so theat is the least threfore it is b

#### Mr Chicken

##### New Member
mmm... negative g-forces

#### macca202

##### Member
wouldn't be negative yet at (c). But i said (c) (i know im wrong) because tthe book says max g when you come "out" of the dip, so i was unsure where that was!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

#### Mr Chicken

##### New Member
There's no such thing as "negative" g-forces
G-forces are really just a way of measuring gross acceleration, as a pose to net acceleration.
The acceleration being measured may be up - "positive" or down - "negative", but that's really not super relevant for this question anyhow
There isn't anyone out there who still thinks it's C is there?
...
Good then... mission accomplished

#### spice girl

##### magic mirror
Actually there is such a thing as negative g forces.

Imagine yourself on a plane, in the pilot seat, with a seat belt on. You control the plane so that the nose begins to point down. You 'should' experience negative g forces.

#### RageAgainstBOS

##### Member
yes when a pilot points his plane down (from level flight) he/she can experinece up to -2 g's making blood go to his/her head. this is called a redout and im a wannabe fighter piliot flight sim nut.

#### SgtSlick

##### Member
Originally posted by Mr Chicken
G forces are just a way of measuring acceleration!
the only place on a roller coaster than the g forces could possibly be more than 1 is at the turning points on the loops (unless it's a rocket powered roller coaster..?!)
so stop trying to argue that C is correct, it's really not!
Nope, g forces are a measurement of the acceleration due to gravity, which is either positive or negative, ie. its a vector and direction dependant

#### Mr Chicken

##### New Member
Originally posted by SgtSlick

Nope, g forces are a measurement of the acceleration due to gravity, which is either positive or negative, ie. its a vector and direction dependant
G-forces are not a measurment of acceleration due to gravity, they're a measurement of force in comparison to gravitational force.

As for the "negative" g-force debarcle, obviously yes, if you accelerate down you will feel an upwards push - g-forces. But as vectors, there is no ultimate negative or positive, each direction of a g-force is as positive or as negative as any other direction. Calling g-force on a diving fighter pilot negative seems a little ambiguous, and relating it to the "red out" is totally invalid - it would be questionable to suggest negative g-forces are responsible for red-outs and positive g-forces are responsible for black outs...

By the way, if we look back to the question in question, we see that they don't actually ask anything about the direction of g-forces, only the size - tho i'm assuming ppl r done answering that and we've started debating something else here?