Physics students needed

[Rhys]

It's been a long time since high school physics so I need some help. Does anyone know the formula for figuring out how much force (energy, whatever) the train was producing in Spiderman 2 when Spidey stopped it? I know there's got to be a way to figure it, I just can't remember how.

 

Thanks in advance.

[caris]

Re: Physics students needed

 

Momentum = velocity x mass

Force = mass x acceleration

 

Hope either helps.

[Agent X]

Re: Physics students needed

 

Who needs physics when you have Bob Greenwade and Steve Long?

 

They have the stats for a steam locomotive in The Ultimate Vehicle and they have the stats for a subway car in the Hero System Vehicle Sourcebook. There are some other train stats too.

 

I'd use the stats of the subway car. You could use its strength and its movement value to figure what its effective strength was for Spidey to resist.

[freakboy6117]

Re: Physics students needed

 

well i guess you'd want to work out the trains momentum so youd want its mass times its speed that woudl give you the amount of energy needed to stop it of course there woudl be other factors air resistance the friction of the track especially if teh breaks where working etc.

 

ok so rough calculation

two new york subway carriages weigh 74433 Pounds (avoirdupois) which equals 33762.2 Kilograms

 

assumeing teh train was going at 65 miles an hour(just a guess) anyway 65 Miles (statute) per hour equals 29.0576 Meters per second

 

= 87,761.9 joules of energy

 

so yet again its shown spidey has some really sturdy shoulders as his arms weren't ripped out of his shoulders by trying to distribute that much energy. nor when he held up that whole cable car.

[Rhys]

Re: Physics students needed

 

Yeah, I had that conversation with my daughter.

 

so yet again its shown spidey has some really sturdy shoulders as his arms weren't ripped out of his shoulders by trying to distribute that much energy. nor when he held up that whole cable car.

 

 

Thanks to all. I guess this means that trying to build a Spidey who could do that in game terms would mean also having one who could beat up Supes himself.

[Mightybec]

Re: Physics students needed

 

I calculate it out to 13.842 KiloAssbags of energy.

[Agent X]

Re: Physics students needed

 

well i guess you'd want to work out the trains momentum so youd want its mass times its speed that woudl give you the amount of energy needed to stop it of course there woudl be other factors air resistance the friction of the track especially if teh breaks where working etc.

 

ok so rough calculation

two new york subway carriages weigh 74433 Pounds (avoirdupois) which equals 33762.2 Kilograms

 

assumeing teh train was going at 65 miles an hour(just a guess) anyway 65 Miles (statute) per hour equals 29.0576 Meters per second

 

= 87,761.9 joules of energy

 

so yet again its shown spidey has some really sturdy shoulders as his arms weren't ripped out of his shoulders by trying to distribute that much energy. nor when he held up that whole cable car.

But it's not just Spidey, it's gravity and friction. What's the formula for figuring out how many joules of energy nature is taking care of for Spidey?

[Zeropoint]

Re: Physics students needed

 

To start with, the formula for kinetic energy is E = 1/2 * m * v^2. Using the numbers above, this works out to 1.425 x 10^7 joules. That's fourteen and a quarter million joules.

 

But let's take a different approach. Assume Spiderman brings the train to a stop in twelve seconds (I'm just pulling this number out ot the air--watching the movie with a stopwatch would give you a much more accurate final result). This gives us an acceleration of 29.0576/12 = 2.421 m/s^2. (Incidentally, this is about 1/4 g)

 

Force = mass x acceleration = 33762.2 x 2.421 = 81740 Newtons. So how much is that? A Newton, the unit of force in the metric system, is the amount of force which will cause one kilogram of mass to accelerate at one meter per second per second. At the surface of the Earth, gravity imparts about 9.81 m/s^2 acceleration, meaning that a kilogram weighs 9.81 Newtons. So, exerting 81740 Newtons of force is equivalent to holding up 81740/9.81 = 8332 kg, or 8.332 metric tons. This works out to a STR of about 43 or so.

 

You could also just multiply the mass of the train by its acceleration in gravities for the same result: 33762.2 x (2.421/9.81) = 8332.

 

For Spidey's actual STR score, consider that he may have been Pushing and adjust accordingly.

 

Zeropoint

[McCoy]

Re: Physics students needed

 

But it's not just Spidey' date=' it's gravity and friction. What's the formula for figuring out how many joules of energy nature is taking care of for Spidey?[/quote']

IIRC the brakes were gone. The track is designed to minimize friction. The experimental method is to get the train up to speed, cut the power, and measure the length it takes for it to cost to a stop on a level track.

 

To get the air resistance, we have to know the temperature and relative humidity that day. New York is close enough to sea level that we can discount the effects of elevation.

 

WAG, I would say probably >5%.

[freakboy6117]

Re: Physics students needed

 

teh scene also shows spidey hasnt been paying attetion in basic physics as wel as doc conners class. sensible thing he could do was tie the two strands of webbing together and then fire more but then it wouldnt have been such a challenge.

 

just out of curiosity some one with better sciencefu than me tell me if the elasticity of the webbing would have been an issue?

[Agemegos]

Re: Physics students needed

 

two new york subway carriages weigh 74433 Pounds (avoirdupois) which equals 33762.2 Kilograms

 

assumeing teh train was going at 65 miles an hour(just a guess) anyway 65 Miles (statute) per hour equals 29.0576 Meters per second

 

= 87,761.9 joules of energy

 

E = 0.5 m v^2

= 0.5 * 33 760 * 29.06^2

= 16 880 * 844.5

= 14,255,160 J

 

That's about 11 million foot-pounds.

 

14.3 megajoules. About the energy that a standard 100-kg Hero has if dropped from a height of 14.3 km (nine miles). Roughly 11,000 times the muzzle energy of a .44 Magnum.

[Killer Shrike]

Re: Physics students needed

 

To start with, the formula for kinetic energy is E = 1/2 * m * v^2. Using the numbers above, this works out to 1.425 x 10^7 joules. That's fourteen and a quarter million joules.

 

But let's take a different approach. Assume Spiderman brings the train to a stop in twelve seconds (I'm just pulling this number out ot the air--watching the movie with a stopwatch would give you a much more accurate final result). This gives us an acceleration of 29.0576/12 = 2.421 m/s^2. (Incidentally, this is about 1/4 g)

 

Force = mass x acceleration = 33762.2 x 2.421 = 81740 Newtons. So how much is that? A Newton, the unit of force in the metric system, is the amount of force which will cause one kilogram of mass to accelerate at one meter per second per second. At the surface of the Earth, gravity imparts about 9.81 m/s^2 acceleration, meaning that a kilogram weighs 9.81 Newtons. So, exerting 81740 Newtons of force is equivalent to holding up 81740/9.81 = 8332 kg, or 8.332 metric tons. This works out to a STR of about 43 or so.

 

You could also just multiply the mass of the train by its acceleration in gravities for the same result: 33762.2 x (2.421/9.81) = 8332.

 

For Spidey's actual STR score, consider that he may have been Pushing and adjust accordingly.

 

Zeropoint

Hmmm...interesting. Agent X and I pegged Spidey at about 45 STR months ago, others argued for 40, but it looks like this feat might have been in the same ballpark.

 

 

And yes, I would agree that Spidey was pushing in this scene in the Champions sence.

 

Thanx Zeropoint!

[Static UK]

Re: Physics students needed

 

Don't forget that in the movie his first few attempts failed as his webbing broke, but he had still slowed the train down a bit before he actually succeded.

[oberon]

Re: Physics students needed

 

teh scene also shows spidey hasnt been paying attetion in basic physics as wel as doc conners class. sensible thing he could do was tie the two strands of webbing together and then fire more but then it wouldnt have been such a challenge.

 

just out of curiosity some one with better sciencefu than me tell me if the elasticity of the webbing would have been an issue?

Hmm, think back, think back. What did I learn back then?

 

I believe this would have an effect. After all, energy expended in stretching the webbing would be energy lost from the train. How big an effect that would have depends on how strong and elastic Spideys webbing really is. Anyone got a figure on that?

 

oberon

[Agemegos]

Re: Physics students needed

 

I believe this would have an effect. After all' date=' energy expended in stretching the webbing would be energy lost from the train.[/quote']

 

Spidey still has to exert a force on the web equal to the force that the web exerts on the train.

 

How big an effect that would have depends on how strong and elastic Spideys webbing really is. Anyone got a figure on that?

 

The energy stored in an elastic object under deformation is equal to 0.5 k x^2, where k is the Hooke's constant of the object and x its extension. How far did the web stretch?

 

Actually, an inelastic web might be better, since plastic deformation can dissipate energy, whereas elastic deformation simples tores it and tries hard to give it back (as anyone who has been stung by a snapping rubber band can tell). The strands in actual spider's webs are not elastic: they extend to a remarkable degree, but the restoring force is not proportional to the deformation. If they were elastic a lot of flying insects would bounce off a spider web as though off a trampoline.

[McCoy]

Re: Physics students needed

 

just out of curiosity some one with better sciencefu than me tell me if the elasticity of the webbing would have been an issue?

It would have been the difference between jumping off a hundred foot bridge with and without a bungee cord. If the webbing had no give, it would have been the same as slaming the train into a wall, the g-force of deacceleration would have been harmful to the passengers. The elasticity of the webbing allowed the train to deaccelerate over time, 12 seconds sounds right, which reduces the g-force on the passengers quite a bit.

[freakboy6117]

Re: Physics students needed

 

yes i guess the webbing must have exceeded its elastic limit or the train would have been dragged back.

[Vorsch]

Re: Physics students needed

 

There is the minor detail that the train is still under power.

 

seems a feat that i would put out of Spidermans strength and toughness range.

 

But i liked it anyway

[Xavier]

Re: Physics students needed

 

Man! I feel smart when I come and hang out here. I understand most of what I read, but alas I can offer nothing of value here

 

I bow before those who are mental giants. I'll happily toil away in your shadow with my etch-a-sketch.

[McCoy]

Re: Physics students needed

 

There is the minor detail that the train is still under power.

 

seems a feat that i would put out of Spidermans strength and toughness range.

 

But i liked it anyway

Thought the engeneer was able to cut the power but not engage the brakes, but I could be wrong.

[SuperBlue]

Re: Physics students needed

 

Let us not forget, his webbing has a tensile Strength of Steel (from one of the spiders used to create the super-spider in the first movie).

 

Considering his webbing is about as thick as yarn... whatever the tensile Strength of woven steel measuring that thickness would give us an idea of how much strain his webbing can take.

 

Also, the buildings he webbed to were what broke, not the webbing itself. So you'd also have to figure out how much strain the buildings could take.

 

In HERO Terms, brick walls are DEF 5 BOD 3, and Concrete Walls are DEF 6 BOD 5...

 

And judging by the way GG tore apart Spidey's webbing at the end of the first movie, I'd have to say that his webbing would prolly be about 8 DEF and 5 BOD... not really sure, cuz the Goblin tore it down pretty easily.

[SuperBlue]

Re: Physics students needed

 

Thought the engeneer was able to cut the power but not engage the brakes' date=' but I could be wrong.[/quote']

 

I do believe you are correct.