Supers Math Headaches

[Kent Allard]

I have a PC with magnetism/telekinesis powers as well as Gravity powers (with
the 10 second persistence modifier). Until now the player has been content to
negate gravity on targets and let them accelerate up and then fall back down,
making the math for damages fast and painless (I've created calculators on my
computer to make this even quicker).

Now he wants to gravity things and swing them via his magnetic powers in effect
working as a catapult. He's thinking in terms of reducing Gravity on a dump
truck to 10 lb. (persistant=10seconds) and throwing it. It would accelerate very
quickly up to the limit of his magnetic range (20 yards). And at 11 seconds it
would become much heavier. And he thinks it would no longer be accelerating but
should therefore continue on it¹s trajectory.

I doubt this, but I'm no math whizz and never took physics so this is a bit
beyond me. Are there any basic rules (or a simple math formula) that I can plug
variables into and get a gameable result that's quick and also reasonable within
the restrictions of the GURPS rules?

Thanks in advance for any wisdom.

[Bent C Dalager]

Post by Kent Allard
Now he wants to gravity things and swing them via his magnetic powers in effect
working as a catapult. He's thinking in terms of reducing Gravity on a dump
truck to 10 lb. (persistant=10seconds) and throwing it. It would accelerate very
quickly up to the limit of his magnetic range (20 yards).

You probably want to differentiate between mass and weight at this
point. Presumably, the gravitic power only reduces weight but keeps
the mass the same. It's the mass that makes an object difficult to
accelerate and so the catapult effect would not be massively aided by
the reduction of the truck's weight.

Cheers,
Bent D

[Tim Little]

He's thinking in terms of reducing Gravity on a dump truck to
10 lb. (persistant=10seconds) and throwing it.

It may have a weight (gravitational attraction) of 10 lb, but still
has a mass of tonnes. It would take a *lot* of force to get it moving
at high speed in a short distance. What force can his magnetic power
exert?

If you want a rule-of-thumb, the amount of kinetic energy he can put
into the dump truck is no more than he could put into a smaller object
without the contragrav. The dump truck will be much more massive, but
also slower. The range will also be a lot less.

[George W Harris]

On Fri, 07 Jan 2011 16:16:37 -0500, Kent Allard

Post by Kent Allard
I have a PC with magnetism/telekinesis powers as well as Gravity powers (with
the 10 second persistence modifier). Until now the player has been content to
negate gravity on targets and let them accelerate up and then fall back down,
making the math for damages fast and painless (I've created calculators on my
computer to make this even quicker).
Now he wants to gravity things and swing them via his magnetic powers in effect
working as a catapult. He's thinking in terms of reducing Gravity on a dump
truck to 10 lb. (persistant=10seconds) and throwing it. It would accelerate very
quickly up to the limit of his magnetic range (20 yards). And at 11 seconds it
would become much heavier. And he thinks it would no longer be accelerating but
should therefore continue on it¹s trajectory.
I doubt this, but I'm no math whizz and never took physics so this is a bit
beyond me. Are there any basic rules (or a simple math formula) that I can plug
variables into and get a gameable result that's quick and also reasonable within
the restrictions of the GURPS rules?

GURPS powers are basically magic, so you can't
really apply real world physical principals to them to get
an answer. You're also going to have to discard relativity.
What you should do is decide which of {velocity, momentum,
energy} you want conserved. He's assuming velocity.

Post by Kent Allard
Thanks in advance for any wisdom.

--
"Doesn't the fact that there are *exactly* fifty states seem a little suspicious?"

George W. Harris For actual email address, replace each 'u' with an 'i'

[tussock]

Post by Kent Allard
Thanks in advance for any wisdom.

The others are right about mass. In a zero g environment, you can
move a big truck easily, but only accelerate it very slowly. It's a lot
like pushing a boat through in the water.

Now, you might still work out how fast you can accelerate the truck
by division. Lifting it with reverse gravity and guiding it to fall
nearby with magnetism might work, letting him tip over and drop
dumptrucks on people's heads if they happen to stand close enough to
one. Not everyone will be able to lift it back off even if it doesn't
kill them.

[Kent Allard]

Thanks guys. I may post the question to the boards on the SJG site in the hopes
of getting more eyes on the problem and have more of a consensus as to how this
should work.