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Old 01-03-2024, 01:26 AM   #1
NMosaic
 
Join Date: May 2021
Default Gravity and Basic Lift

Hello just a very quick question, under RAW it gives rules for every activity that's affected by different gravity: Encumbrance, Jumping, Throwing, and Falling; but surprisingly LIFTING is left out. Now I ain't an astrophysicist, my main forte is electricity more than mechanics, but last I remember in physics class is that lifting is different in an other gravity. So is there like a physical reason or in-game reason it's not affected RAW, or is there something I'm completely missing. Let me know.
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Old 01-03-2024, 05:09 AM   #2
Varyon
 
Join Date: Jun 2013
Default Re: Gravity and Basic Lift

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Originally Posted by NMosaic View Post
Hello just a very quick question, under RAW it gives rules for every activity that's affected by different gravity: Encumbrance, Jumping, Throwing, and Falling; but surprisingly LIFTING is left out. Now I ain't an astrophysicist, my main forte is electricity more than mechanics, but last I remember in physics class is that lifting is different in an other gravity. So is there like a physical reason or in-game reason it's not affected RAW, or is there something I'm completely missing. Let me know.
So long as it isn't a microgravity or zero gravity situation, you can generally get away with just treating everything as weighing its normal weight multiplied by the local gravity. So if you have BL 20, you can lift a 20 lb object overhead with one hand in one second - and an object that is 40 lb in 1G would only be 20 lb in 0.5G and thus you could lift it, while an object that is 10 lb in 1G would be 20 lb in 2G, and thus would be at the limit of what you can lift in this fashion.
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Old 01-03-2024, 08:25 AM   #3
Anaraxes
 
Join Date: Sep 2007
Default Re: Gravity and Basic Lift

Campaigns, B350, the box titled "Different Gravity".

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Originally Posted by B350
In higher or lower gravity, mass stays the same, but weight changes.

If local gravity is more than 1G, multiply the sum of your body weight and the weight of everything you’re carrying by (local gravity in Gs)-1. This is the extra weight you’re carrying due to high gravity.

If local gravity is less than 1G, multiply the weight of the gear you’re carrying by the local gravity, and use the modified weight to determine your encumbrance.
And so on. If you lift something, you'd be carrying it, so lifting seems covered at least indirectly.

I don't see an explicit directive to change Basic Lift; instead, you change the current effective weights of whatever you're lifting to compare to (standard 1G) BL. Whichever makes more sense to you, I suppose.
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Old 01-03-2024, 10:32 AM   #4
NMosaic
 
Join Date: May 2021
Default Re: Gravity and Basic Lift

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Originally Posted by Anaraxes View Post
Campaigns, B350, the box titled "Different Gravity".

And so on. If you lift something, you'd be carrying it, so lifting seems covered at least indirectly.

I don't see an explicit directive to change Basic Lift; instead, you change the current effective weights of whatever you're lifting to compare to (standard 1G) BL. Whichever makes more sense to you, I suppose.
Thank you, but what about microgravity or zero G? How will basic lift, and for that matter encumbrance, work?
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Old 01-03-2024, 11:01 AM   #5
Varyon
 
Join Date: Jun 2013
Default Re: Gravity and Basic Lift

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Originally Posted by NMosaic View Post
Thank you, but what about microgravity or zero G? How will basic lift, and for that matter encumbrance, work?
Things would be much more complicated in zero G, where what you're dealing with is mass rather than weight. The simplified version is that something that weighs less than you can be moved, while something that weighs more than you cannot (you end up moving instead). More realistically, in either case both you and the object move, in opposite directions, and the one that weighs more moves less (with extreme differences, to the extent it might as well not move at all). But then if you can brace against something markedly heavier than the object you're moving, you can move anything... eventually. I really don't know how to calculate that, though... maybe (just grabbing at numbers here) anything that fits within your BL at 0.1G can be lifted above your head in a second, while anything heavier takes seconds equal to (0.1G weight)/BL. But zero G is really complicated to work out at the table, I think, which is probably why the Basic Set rules are really simple there. I forget if GURPS Space has any further guidance here.
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Old 01-03-2024, 10:34 PM   #6
Pursuivant
 
Join Date: Apr 2005
Default Re: Gravity and Basic Lift

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Originally Posted by Varyon View Post
But zero G is really complicated to work out at the table, I think, which is probably why the Basic Set rules are really simple there. I forget if GURPS Space has any further guidance here.
None in the GURPS 4E version of Space.

I was going to propose similar mechanics for shifting objects in zero G, but Varyon beat me to it.

If you're braced against an extremely heavy object, you can theoretically push or shift far more mass than normal. As a guess, I'd make the maximum amount of mass you can shift in microgravity equal to the mass you can shift slightly (BL x 50).

The maximum mass you can push hard enough when braced that it does damage when it hits is BL x 8 (based on the Throwing Damage table on p. B335). After that, treat a collision with a moving object in free fall as a Slam, with the object's speed being equal to 1 yard/sec. divided by the number of seconds it took you to accelerate it.

As SWAG rules for moving lighter or heavier objects in free fall when you're not braced:

Object is up to 10% of your mass: Use the normal lifting or throwing rules. Roll vs. Free Fall skill to retain control of your motion if you throw an object at speed.

Object is up to 50% of your mass: Roll vs. Free Fall skill at -2 per 10% of your mass the object weighs beyond 10%. Success means that you are pushed backwards at 25% of maximum speed at which you could push the object, while it goes in the opposite direction at 75% of maximum speed. Failure means both you and the object are pushed back at the half maximum speed traveling in opposite directions.

Object is up to 100% of your mass: As above, but -2 per 10% the object weighs over 50% of your mass. Success means you're pushed back at 75% of normal speed, while it is pushed in the opposite direction at 25% of normal. Failure means you push off the object traveling backward at the 90% of normal speed while it goes in the opposite direction at 10% of normal.

Object is over 100% of your mass: You can push off the object to move at any rate between 1 yard/sec. and half your normal Move (plus any modifications for Enhanced Move in Free Fall). It is very slowly pushed in the opposite direction at the rate of just a few inches per second.

Object is over 50 times your mass: It is effectively a solid surface. You can push off of it at full speed and it will barely move.

Roll vs. Free Fall to control your facing following an unexpected push-off from an object.

Realistic rules are a physics problem.

Last edited by Pursuivant; 01-03-2024 at 11:14 PM.
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Old 01-03-2024, 11:09 PM   #7
Fred Brackin
 
Join Date: Aug 2007
Default Re: Gravity and Basic Lift

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Originally Posted by Pursuivant View Post
. If unsupported, you are limited to shifting items with much smaller mass than your own, otherwise, the object effectively stays still while you push off from it or you and the object go in opposite directions. .
There will be no staying still. If you and the object are in contact while floating in mid "air" (or of course, mid-vacuum) in zero G the equal and opposite reaction law will be in full effect.

For example, you are in contact with a mass 10x your own. You push off from it. Without Super Jump your velocity will be your Base Speed (5 for an average human). The object will be moving in the opposite direction at the same speed multiplied by the ratio of your' mass divided to its' mass. i.e you're going in one direction at 5 and the object is going in the opposite direction at 0.5 yards per second.
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Old 01-05-2024, 07:36 PM   #8
Pursuivant
 
Join Date: Apr 2005
Default Re: Gravity and Basic Lift

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Originally Posted by Fred Brackin View Post
There will be no staying still. If you and the object are in contact while floating in mid "air" (or of course, mid-vacuum) in zero G the equal and opposite reaction law will be in full effect.
Granted that there will be equal and opposite effect, but a successful Free Fall skill roll helps you to counter any unwanted movement. Margin of success determines how well you do it.

It might be on the cinematic side for unassisted counter-movements, but is realistic if you're wearing something like a thruster pack.

Quote:
Originally Posted by Fred Brackin View Post
For example, you are in contact with a mass 10x your own. You push off from it. Without Super Jump your velocity will be your Base Speed (5 for an average human). The object will be moving in the opposite direction at the same speed multiplied by the ratio of your' mass divided to its' mass. i.e you're going in one direction at 5 and the object is going in the opposite direction at 0.5 yards per second.
That's accurate and simple, but a Free Fall skill roll should let you set your velocity to anything up to your Basic Speed, with correspondingly less movement from the object you're pushing off of.

In any case, this discussion has made me realize that the basic rules for moving and fighting in microgravity could be expanded. A running fight using melee or thrown weapons in microgravity would be lots of fun, especially if there were large floating objects (e.g., cargo containers) to serve as cover, push-off points and improvised weapons. The trick is to keep the rules from becoming an exercise in vector mechanics.
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Old 01-05-2024, 07:52 PM   #9
Ulzgoroth
 
Join Date: Jul 2008
Default Re: Gravity and Basic Lift

In microgravity there's no substantive limit on what speed you can get things to move at regardless of how massive they are, but dragging along extra mass would certainly impact your ability to accelerate quickly, both in the 'basic speed' sense and in terms of things like dodging.

You could plausibly singlehandedly push an MBT up to running-like speed, but strapping on a field pack will still make your life harder.
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Old 01-05-2024, 09:45 PM   #10
Pursuivant
 
Join Date: Apr 2005
Default Re: Gravity and Basic Lift

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In microgravity there's no substantive limit on what speed you can get things to move at regardless of how massive they are, but dragging along extra mass would certainly impact your ability to accelerate quickly, both in the 'basic speed' sense and in terms of things like dodging.
True, as long as you're in vacuum.

Vacuum makes the calculations simpler, microgravity plus atmosphere (e.g., inside a giant space station) massively complicates the physics, but makes movement more interesting due to drag effects.
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