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mass = 1 ... Real weight equivalent ?


Andy Gilbert
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But to be a little off-top, I keep seeing the misconception that hammers and feathers fall at the same rate in a vacuum. Which would be true if the objects didn't have mass. But a Hammer or Piano has a substantially greater gravitational field than a feather. They would actually fall faster, just not on a scale you would notice. But it's important if you plan on throwing large objects at nearby planets.

More force does not mean greater speed. More force is exerted, but because the heavier object has more mass, more force is required to move it. Barring air resistance, a heavy object and a light object fall at the exact same speed. When you consider air resistance, the shape and mass of an object become factors. For example, a person wearing a parachute is much heavier than a brick, but the brick will fall faster.

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If I could make a suggestion to the topic starter, add some key commands to adjust various properties such as mass, damping, (spring height etc if a vehicle) so you can fine tune how it plays so you're not always having to stop, re-edit and try again. Not only will it help you find good values for your objects behavior, but it can be great fun too. (Set the spring height of a vehicle to stupidly large values and let the Whacky Races begin).

 

 

I didn't notice the funny gravity, I set it manually anyway but I'll have to go and check it now (everything seems to fly-drive as before).

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More force does not mean greater speed. More force is exerted, but because the heavier object has more mass, more force is required to move it. Barring air resistance, a heavy object and a light object fall at the exact same speed. When you consider air resistance, the shape and mass of an object become factors. For example, a person wearing a parachute is much heavier than a brick, but the brick will fall faster.

 

Now... you see that confuses me? Im sure your right and it just my physics math thats **** but... if i hold to small boxes, same size same shape exactly the same but one is full of stones the other isnt and i drop them both from the same height.. which one will get the floor first? Im sure if they had long enough to fall they will reach max velocity and be falling the same but the weight one will initially fall faster?

 

Andy

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Now... you see that confuses me? Im sure your right and it just my physics math thats **** but... if i hold to small boxes, same size same shape exactly the same but one is full of stones the other isnt and i drop them both from the same height.. which one will get the floor first? Im sure if they had long enough to fall they will reach max velocity and be falling the same but the weight one will initially fall faster?

 

Andy

 

The mass of the objects makes no difference to free falling objects. If you look at the equation for the time taken for an object to fall from some arbitrary height you will see that mass does not even enter into the equation. Here on earth they will fall differently due to air resistance.

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The mass of the objects makes no difference to free falling objects. If you look at the equation for the time taken for an object to fall from some arbitrary height you will see that mass does not even enter into the equation. Here on earth they will fall differently due to air resistance.

 

?? Does it not? Wiki...

Equations for a falling body

Under normal earth-bound conditions, when objects move owing to a constant gravitational force a set of dynamical equations describe the resultant trajectories. For example, Newton's law of universal gravitation simplifies to F = mg, where m is the mass of the body. This assumption is reasonable for objects falling to earth over the relatively short vertical distances of our everyday experience, but is very much untrue over larger distances, such as spacecraft trajectories

 

Again i might be wrong.

 

And isnt the equation for working out "time taken" T = D/S (V). V being velocity where the equation for velocity involves Mass?

 

Andy

The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do.

 

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Again i might be wrong.

 

And isnt the equation for working out "time taken" T = D/S (V). V being velocity where the equation for velocity involves Mass?

 

Andy

 

 

 

 

wow it's turned into the Fizzsicks thread lol ... what equation are you using for Velocity?

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Note, Newton had no concept of air resistance, dampening, etc. in his time, so his equations do not reflect that.

 

Einstein proved his equations or "laws" (quote unquote) break down in non-Earth conditions.

 

You need to go by universal laws of gravitation, not Earth laws.

 

 

 

In retrospect, Newton's equations will work fine in game calculations as long as you ensure that the velocity has already been weighted by the factors necessary, including but not limiting to: static friction, kinetic friction, air resistance, host fluid viscosity, spring dampening, etc. etc. etc.

 

As you can see, there are loads of factors that affect the fall time of objects. A lot of assumptions are made when those equations are presented to you in those simple forms. Force doesn't equal Mass times Gravity ALWAYS. Distance doesn't equal Rate times Time ALWAYS.

 

Things like this crack me up, I had a 30 minute discussion with the Algebra II teacher about this:

We were being taught the equation to calculate the ending height of an object that is dropped with no initial velocity. It is:

end height = -16 * time ^ 2 + initial height.

 

My first question, or rather statement, was "That can't be right? It doesn't take into account any physical properties of the object." The discussion continued with specifics, until I had pissed off every student in the class and had still not gotten anywhere. It basically equated to the teacher denying that physics has any impact on math...

 

Lol,

Tyler

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wow it's turned into the Fizzsicks thread lol ... what equation are you using for Velocity?

 

lol yeh it has. And sorry i was refering to Termnal Velocity, which is different.

 

anyways, its been an interesting topic, ill just carry on with what im doing. lol. I only asked whilst at work and was "thinking" about it. Less thinking more doing!

 

n retrospect, Newton's equations will work fine in game calculations as long as you ensure that the velocity has already been weighted by the factors necessary, including but not limiting to: static friction, kinetic friction, air resistance, host fluid viscosity, spring dampening, etc. etc. etc.

 

As you can see, there are loads of factors that affect the fall time of objects. A lot of assumptions are made when those equations are presented to you in those simple forms. Force doesn't equal Mass times Gravity ALWAYS. Distance doesn't equal Rate times Time ALWAYS.

 

Things like this crack me up, I had a 30 minute discussion with the Algebra II teacher about this:

We were being taught the equation to calculate the ending height of an object that is dropped with no initial velocity. It is:

end height = -16 * time ^ 2 + initial height.

 

My first question, or rather statement, was "That can't be right? It doesn't take into account any physical properties of the object." The discussion continued with specifics, until I had pissed off every student in the class and had still not gotten anywhere. It basically equated to the teacher denying that physics has any impact on math...

 

Lol,

Tyler

 

lol, i know what you mean. Its to much a wider subject and can go on and on and on. A bit like when i start thinking..whats beyond space or does it end and how big is it? (it winds me up even thinking about!)

 

Anyways, like i said, ill just carry on as i am! :)

 

Cheers

Andy

The good news about computers is that they do what you tell them to do. The bad news is that they do what you tell them to do.

 

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The acceleration of bodies due to gravity is uneffected by their mass and in a vacuum the velocity of a light and a heavy body affected by the same gravitational force would always be the same for either body at any given point in time. In the real world air resistance etc has a dampening effect on bodies and aero dynamics come into play resulting in terminal velocities being reached and a constant velocity with no further acceleartion and these differ from object to object.

 

Mass really comes into effect where momentum is concerned, and especially the transfer of momentum between bodies. However, so long as the differences between the masses of objects is proportional (say between a bullet and a tin can) then it really doesn't matter if a simulation makes the bullet a gram in weight or a ton so long as the tin can is made 20 grams or twenty tons respectively). It's all relative. This is where your F = ma comes in. Its all about the forces involved and the transmission of forces when items collide. It's the force thats created by the deacceleration of the bullet hitting the can that provides the force to accelerate the can with a much larger mass and cause it to move (with a much lower velocity than the colliding bullet of course).

 

So although falling bodies under gravity accelerate at the same rate regardless of their mass, the momentum of the falling bodies is affected by their mass and the heavier object will have the greater momentum and will impart a far great force when colliding with something than the lighter body.

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?? Does it not? Wiki...

 

 

Again i might be wrong.

 

And isnt the equation for working out "time taken" T = D/S (V). V being velocity where the equation for velocity involves Mass?

 

Andy

 

Given Distance (d) = Rate (Properly called "Speed", denoted s or r) * Time (t), you get d = rt.

 

You can derive:

Rate = Distance / Time

Time = Distance / Rate

 

All of which are true. Just remember that you can substitute Speed for Rate, but NOT Velocity. Speed and Velocity are NOT the same, nor is Acceleration.

 

Things to note:

Velocity - Type: Vector - Has: Direction, Magnitude

Speed - Type: Magnitude Quantity - Is: The magnitude of velocity

Acceleration - Type: Vector - Is: Velocity over Time

 

Speed is your Distance over your Time, or how far you have traveled in a given amount of time.

Velocity is your Speed with your Direction. A change in speed is a change in velocity, but a change in velocity's direction only is not a change in speed. For example, a velocity of (1,0,0) and (0,1,0) have the same Speed (1 unit per second), but a different direction. The first is moving +X, the second is +y.

 

Acceleration is the first order derivative of the same equation, giving your Velocity over Time. It is given in terms of distance units over time units squared. i.e. -9.8 m/s^2 is acceleration due to gravity at sea level.

 

So to sum:

Speed - Rate of change in motion. It is a scalar quantity with the dimensions distance/time. It is measured in the same units as velocity, but has no direction.

Velocity - Both direction and magnitude (Speed) of motion.

Acceleration - Rate of change in velocity.

 

Links: http://www.edinformatics.com/math_science/acceleration.htm

Links for people who like math notation as opposed to English words:

http://en.wikipedia.org/wiki/Velocity

http://en.wikipedia.org/wiki/Acceleration

http://en.wikipedia.org/wiki/Speed

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YES!

 

Terminal velocity is the only condition where any and all objects fall at the same rate and have the same time. Sorry about the above post by me with the math rants, it was meant to be after my first one, I hadn't expected two people to respond so quickly.

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What if a black hole is dragged into another black hole, wouldn't there the terminal velocity exceed lightspeed, since space and time is bent, so that no other object could even come close to reaching the same terminal velocity being dragged in either black hole?

Newton's formula lacks that component. However, if you use Newton's formula of gravitational force between two masses, and assume the distance is limes 0, you get also very interesting results :)

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So are we agreed? SetBodyMass(1) = 1kg? :)

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I have no idea what a kg is. I know it's 1000 grams, but I don't know how much that weighs.

 

 

About 2.2 lbs in "old" money :)

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Well if I can remember this correctly from school. 1 liter of water = 1kg at sea level.

So if you have 10kg of water you have 10 liters of water, and opposite, 10 liters of water would weigh 10 kg.

 

This would of course take into consideration that you do NOT use heavy water! besides that would be very dangerous.

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Well if I can remember this correctly from school. 1 liter of water = 1kg at sea level.

So if you have 10kg of water you have 10 liters of water, and opposite, 10 liters of water would weigh 10 kg.

 

This would of course take into consideration that you do NOT use heavy water! besides that would be very dangerous.

 

 

Heavy water is mildly toxic if ingested ..dangerous when ingested in in large amounts ..

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  • 3 months later...

Dark matter still sounds to me like a mathematical work around to me.

 

...Kind of like the "superluminous ether" that was conjured to define a medium for light to travel through. This was before Maxwell came up with the laws that related Electricity and Magnetism.

 

Also, the effects you are talking about would have to be so small that its not necessary to account for. For example, we don't need modern physics (relativistic physics) to explain why an airplane flies or a ball falls. So, unless you are modelling something subatomic or travelling at >.1 the speed of light, Newtonian mechanics work fine. The issue is not mass, but air resistance when something falls. Otherwise, the hammer and the feather would fall at the same rate. It can be demonstrated over and over again in a vaccum chamber, or as we saw in the moon landings - assuming you are not one of those people that think we faked it. ;)

 

In a game, it just needs to be fun. :) Not physically perfect. My two cents.

 

 

 

Actually Flexman is right, the gravitational pull makes heavier object fall faster. In addition there is no such thing as vacuum, as 90% of the universe is dark matter. Dark Matter has just the same kind of resistance as air, but of course much lower, so the shape and size of bodies matters also when they fall through dark matter.

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I couldn't agree more. Dark matter is just more sticking plaster desperately trying to hold together an outdated model of the Universe that no longer matches the observable behaviour. Science and mathematics being reflections of the less than perfect human mind always produce less than perfect models ... but we have a fun time trying to convince our selves we can explain everything. However, we might as well spend our time on the planet doing something and there is nothing we love to do more than re-create everything that our sensory perceptions lead to to believe exist ... be it in the form of a mathematical description of the Universe or a digital representation of the world in the form of a computer game :)

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Now... you see that confuses me? Im sure your right and it just my physics math thats **** but... if i hold to small boxes, same size same shape exactly the same but one is full of stones the other isnt and i drop them both from the same height.. which one will get the floor first? Im sure if they had long enough to fall they will reach max velocity and be falling the same but the weight one will initially fall faster?

 

Andy

 

here's my take on it:

 

the cardboard box is not air tight and even if it were airtight you'd still have to account for the fact that here on earth all objects are submerged inside of a gigantic sea of air, and therefore a sort of gaseous buoyancy becomes a factor particularly when you are speaking of gas molecules such as helium or just normal air trapped inside of an airtight cardboard box. And the box that has more air inside is going to become more buoyant. Therefore it actually has forces which are acting against the "pull straight down effect" of gravity, it's not that gravity is acting on the box any less than the one that is filled with stones, it's just gravity is behaving differently because the composition of the two object/mixtures is different.

 

am i completely off base here :)

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doh ... you've started another round off again ;) Lumooja will be posting about not having taken into account the effects of tachions spiralling backwards from the future :)

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