Center of mass
234
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10
EPISODES
7
PODCASTS
Search complete. 234 mentions across 10 episodes found for "Center of mass".
Oct 9, 2026
speaker_4HOST
Mm-hmm.
speaker_3HOST
And because of all that sloshing weight, the Earth, its center of mass-like, its actual gravitational heart, isn't actually located where its geometric center is.
speaker_4HOST
No, it's not.
speaker_4HOST
Not at all.
speaker_4HOST
We are talking about two very different points.
speaker_3HOST
Okay.
speaker_4HOST
You have the geometric center, and you have the center of mass.
speaker_4HOST
So the geometric center, which scientists sometimes call the center of figure, is, uh, it's purely about shape and volume.
Sean Patrick MacDonaldGUEST
One is the approach to moving the cockpit has remained the same since the 1998 prototype.
Sean Patrick MacDonaldGUEST
We rotate the cockpit at its center of mass.
Sean Patrick MacDonaldGUEST
So there's I think it's an abstract concept.
Sean Patrick MacDonaldGUEST
I've always tried to develop ways for for anyone to kind of have that.
Sean Patrick MacDonaldGUEST
Aha, I understand moment.
Sean Patrick MacDonaldGUEST
So.
Sean Patrick MacDonaldGUEST
If you rotate a cockpit at the center of mass, let's say you support the cockpit at the center of mass, you can actually move it with very little force because it's essentially, it's supported on a system that's designed to actually hold the weight, right? All the weights on bearings, right? So if you have this 600 pounds in the middle and you find where the center of mass of the 600 pounds is and you support it there and you mechanically link to it, You can go up to it and you can push your finger on it.
Sean Patrick MacDonaldGUEST
It'll rotate around that axis.
Ramamurti ShankarHOST
This rod will still rotate.
Ramamurti ShankarHOST
It is still true that when the total force adds up to zero, the center of mass will not accelerate, but that doesn't mean the body will not move, because keeping the center of mass fixed, All right, so you have to ask yourself, what does it take to keep it from rotating? Then we know that the cause of rotation is the torque.
Ramamurti ShankarHOST
So, I'm going to write down now the conditions for a body, a planar body lying in the plane of the blackboard, to stay still and not move.
Ramamurti ShankarHOST
They are that all the forces in the x direction.
Ramamurti ShankarHOST
That should add up to zero.
Ramamurti ShankarHOST
All the forces in the y direction, that should add up to zero.
Ramamurti ShankarHOST
This will make sure the center of mass as a whole is not going anywhere.
Ramamurti ShankarHOST
And finally, to keep the body from moving or spinning, all the torques should add up to zero.
Kramer AmmonsGUEST
rabbit hole, took off diving deep.
Kramer AmmonsGUEST
And I'm like, what is the best way? And it's a very simple answer, like the center of your mass, which I'm like, okay, where's the center of mass? And it's like, okay, well, what's your body type? You know, guys who have a lot more upper body muscle, it can change a little bit.
Kramer AmmonsGUEST
And so that kind of depends.
Kramer AmmonsGUEST
But generally, it's your belly button, but towards the back of your body.
Scott WarrHOST
You know, Don has a few more years running on his waist or body or whatever you want to call it than I do.
Don FreemanHOST
Why'd you have to go to the waist, Scott? Why'd you go to the waist?
Scott WarrHOST
Center of mass, Freeman.
Scott WarrHOST
Center of mass.
speaker_4HOST
Mm-hmm.
speaker_3HOST
And because of all that sloshing weight, the Earth, its center of mass-like, its actual gravitational heart, isn't actually located where its geometric center is.
speaker_4HOST
No, it's not.
speaker_4HOST
Not at all.
speaker_4HOST
We are talking about two very different points.
speaker_3HOST
Okay.
speaker_4HOST
You have the geometric center, and you have the center of mass.
speaker_4HOST
So the geometric center, which scientists sometimes call the center of figure, is, uh, it's purely about shape and volume.
Tim DennisHOST
You kinda have to get into it a little bit.
Tim DennisHOST
But it says here that Earth's center of mass is moving, and NASA warns that it could wreak havoc on satellite positioning data and navigation systems.
Tim DennisHOST
Now, when I tell you how much it's moving, you may go, "Eh." But it's a real concern, especially since our satellite positioning data and our navigation systems run a lot of stuff on Earth, when you sit and think about it.
Tim DennisHOST
Uh, Earth's center of mass is constantly moving in time with the seasons, experts have revealed.
Tim DennisHOST
A team of n- scientists at NASA said our planet is continually sloshing and sagging under the weight of water, ice, and air.
Tim DennisHOST
Now, when you put it that way, well, okay, haven't we adjusted for that? Well, you can't.
Tim DennisHOST
These are all affected by winter freezes, springtime thaws, churning oceans, and changing atmospheric pressure.
Tim DennisHOST
Because of this, Earth's center of mass swivels around its geometric center by as much as several millimeters, they've revealed, and it could be throwing off satellite data and navigation systems.
speaker_1HOST
That would be disastrous.
Henrik JentschHOST
When the data says the pelvis is shifting toward the target early, does that mean the entire center of mass is shifting? Like, are we talking about an aggressive full body slide to the left?
speaker_1HOST
I'm so glad you brought that up because the source text is very explicit about this distinction.
speaker_1HOST
Pelvis sway is strictly a segment measurement.
Henrik JentschHOST
Meaning it's just tracking the pelvis.
speaker_1HOST
Exactly.
speaker_1HOST
It is not a direct measurement of your entire overall center of mass.
speaker_1HOST
So no, this is absolutely not an invitation to execute a massive upper and lower body slide past the golf ball.
Ramamurti ShankarHOST
I'm going to introduce a new guy, capital X.
Ramamurti ShankarHOST
As you know, that's called the center of mass coordinate, and it's defined as m1 x1 plus m2 x2 divided by capital M.
Ramamurti ShankarHOST
Capital M is just the total If I do that, this is a definition, then we can write this equation as follows.
Ramamurti ShankarHOST
I will write it and then we can take our time seeing that it is correct.
Ramamurti ShankarHOST
That's all I want you to check.
Ramamurti ShankarHOST
So, take this expression, divide by the total mass and multiply by the total mass.
Ramamurti ShankarHOST
Well, the multiplying by the total mass is here, and when divided by the total mass, you get the second derivative of the center of mass coordinate.
Ramamurti ShankarHOST
So, what have I done? I have introduced a fictitious entity,
Ramamurti ShankarHOST
For a continuous distribution of matter, like this one, the sum is replaced by an integral.
Ramamurti ShankarHOST
For example, for a rod, it was ml squared over 12 around one of the ends, around the center of mass.
Ramamurti ShankarHOST
And for a disk, it was mr squared over two.
Ramamurti ShankarHOST
So every body has a moment of inertia.
5 MINS LATER
Ramamurti ShankarHOST
For a rod, I did two calculations.
Ramamurti ShankarHOST
One was around this end, and the moment of inertia around the end was ML squared over three, and the moment of inertia around the center was ML squared over 12.
Ramamurti ShankarHOST
And at the end of the lecture, I said, "Notice the following fact: the moment of inertia through the end and the moment of inertia through the center of mass are related in a very simple way, which is the moment of inertia with respect to the new point, is moment of inertia with respect to the center, plus the mass of the entire rod times the square of the distance, L over two squared, separating the axis going through the center of mass and the new axis." And that's called a parallel axis theorem, and I'm going to show you in general why it is true.
Ramamurti ShankarHOST
The parallel axis theorem says that if you know the moment of inertia through the center of mass, you are done.
RustageHOST
Your ray blade.
ShwabadiPANELIST
I, I'm just going c- center of mass
RustageHOST
... shines with orange light.
RustageHOST
Center of mass.
RustageHOST
You hit metal, but he grins a wolfish grin as he looks down at you.
ShwabadiPANELIST
Oh, God.