Recent content by Ketman

That's interesting to know. I didn't imagine it would last that long. I've found a couple of links to it, so I'll give those a read. Thanks.

Perhaps you are not aware of how essential sheep were to the economies of the ancient world, and how numerous they were. If it hadn't been for wool, the Romans would have frozen to death. In ancient times, at least in the west, not only was wool the most common material for making clothes, it...

No, a mass of sodden wool wouldn't be good. But probably no worse than a mass of sodden straw. That's why a waterproof inner layer would be desirable. Still, thanks for the link, which I hadn't seen before. What I had in mind was the transportation of smaller amounts than would be stored in an...

In those days ice was transported from mountain regions to towns and cities, so that, for example, wealthy families could have interesting desserts at their banquets. And I imagine some market-sellers might have used it to keep their produce fresh - displaying sea-food in an ice-tray, for...

I thought this was already settled. There is no expenditure of energy. If that were not so, there would be energy loss in the case I theorized where the weight came down in a curve because the rod was constrained at the other end. It would arrive with less kinetic energy, and therefore less...

Not really. I'm satisfied that the right way is to put wheels on the trebuchet, though that's more a practical constructor's solution than a physics solution. If you could guarantee complete rigidity in your frame, the fixed-frame machine might be just as good. But the time and materials...

...the difference being that the latter scenario uses up no energy. The two cases I explored produce an equivalent result because of that. In the first case, resistance to movement is 0%. In the second, it's 100%. The result in both cases is that energy is 100% conserved.

Thanks for the replies. The thought of "no cost" horizontal translation of an object under gravity occurred to me as a result of looking into trebuchets. A trebuchet is a missile-throwing device, with a heavy counterweight on the short end of a beam that pivots about an axle fixed to a...

Suppose the sphere is rolling to the left. Draw a vertical line through the centre. Every point on the sphere to the right of the line is moving upward, every point to the left is moving downward. The only points on the surface that have zero vertical velocity are the point in contact with the...

You have a weightless rod with a wheel attached to one end (weightless, frictionless) and a weight attached to the other. The weight is mounted on a short axle, and can rotate freely. With the wheel on the floor, the rod is held at 45 degrees to the horizontal and then released. Since the rod...

Sounds like a situation of some gravity to me.

I don't think it's a silly question, but it's more a philosophical question than a scientific one. There are certain qualities in the universe which have no apparent cause. Not just inertia, but time and space, gravity, magnetism, etc. These just have to be called "phenomena". They all come into...

Without wishing to blow more smoke over the question, wouldn't it be true to say that determining the velocities after a collision between two bodies of different materials would depend upon the lower COR of the two? And that in measuring CORs by experiment you'd need a surface with a COR close...

Thanks to dulrich and sithdarth. This is more like it. I think the source of my problem lay in the assumption I had made that steel had a very high coefficient of restitution, and that was why it was the chosen material for those aforementioned executive toys. It certainly seems like a nearly...

Nope. There cannot be a 100% transfer of momentum unless the club comes to a complete halt after impact. So that equation doesn't apply. The question comes down to whether and how the composition of the golf ball increases or decreases the percentage of momentum transferred. But whatever the...