Heavy Ball - Weak Bridge

Originally posted by Nemesio
If it rolled at the speed of light (or very close to it), wouldn't it start to
have increasing mass? Wouldn't that make its weight greater, making
the effect of gravity more significant?

Nemesio

I already pointed that out.

The statement that 'Horizontal motion does not oppose or counter downward forces' is not consistent with the scientific concept of orbital velocity. This states that at a certain speed (which I think would vary with altitude and other factors), the forward momentum is in balance with the downward force of gravity. Weightlessness.

So, simplistically, I would venture that the answer is a speed roughly equal to half the speed of orbital velocity.

Originally posted by wadelog
The statement that 'Horizontal motion does not oppose or counter downward forces' is not consistent with the scientific concept of orbital velocity. This states that at a certain speed (which I think would vary with altitude and other factors), the forward momentum is in balance with the downward force of gravity. Weightlessness.

So, simplistically, I would venture that the answer is a speed roughly equal to half the speed of orbital velocity.

Hey a new entrant....well done

Originally posted by wadelog
The statement that 'Horizontal motion does not oppose or counter downward forces' is not consistent with the scientific concept of orbital velocity. This states that at a certain speed (which I think would vary with altitude and other factors), the forward momentum is in balance with the downward force of gravity. Weightlessness.

So, simplistically, I would venture that the answer is a speed roughly equal to half the speed of orbital velocity.

You mean orbital velocity?

Horizontal motion does not counter downward forces, but it could very well be that the velocity with which the object is moving tangential to the gravitic forces work together to keep it at a constant altitude, although at a constant freefall, and an object moving fast enough will, in fact, escape the pull of gravity.

This is because the gravitic force would shift direction as the object moves forward, being directed at the center of the larger mass, Earth, and not because the motion itself actually reduces the force at all, because if you took a snapshot of an stable orbiting object at any time, gravity isn't being countered by any actual force.

Nonetheless, the orbital effect might should be considered here.

However, orbital velocity tends to be rather high for objects high in the atmosphere though, and close to the Earth, as any bridge would be, such a velocity would be absolutely tremendous.

Originally posted by geepamoogle
You mean orbital velocity?

Horizontal motion does not counter downward forces, but it could very well be that the velocity with which the object is moving tangential to the gravitic forces work together to keep it at a constant altitude, although at a constant freefall, and an object moving fast enough will, in fact, escape the pull of gravity.

T ...[text shortened]... and close to the Earth, as any bridge would be, such a velocity would be absolutely tremendous.

now we're gettin somewhere

"such a velocity would be absolutely tremendous", sure, but I think still trivial when compared against the speed of light, as suggested earlier.

Recall that the problem states 'assume no friction', which would imply that the bridge be inside a vacuum chamber, not likely.

And that the ball doesn't need to enter a state of constant-free-fall [0-G], just to reduce its downward force against the bridge by half [no actual reduction in weight, but a huge increase in momentum away from the deck].

I lack the background in physics to guess if this would equate to half the speed of orbital velocity at sea level, or somewhat faster. If I were a contestant in a game show, I'd go with somewhat faster.

How do you calculate the velocity needed to achieve stable orbit, given the altitude, and the mass of both the object and the planet?

Originally posted by geepamoogle
How do you calculate the velocity needed to achieve stable orbit, given the altitude, and the mass of both the object and the planet?

G = ma = mv^2/r

v =(rG/m)^(1/2)

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

Originally posted by uzless
You are starting to catch on.

The entire bridge will not collapse at the same moment. Only the section of the bridge that the ball is/was on will collapse. By the time the section of the bridge collapses, if the ball is moving fast enough the ball may already be on to the next section of the bridge.

In other words, is it possible for the ball to tr ...[text shortened]... crash through the first section of the bridge regardless of the speed at which it is travelling?

That's ridiclulous. You need more information. If it takes 500 years for one section to collapse, you could roll it at .000001 kph. It it takes 10^-100000000000000000000 nanoseconds to collapse, rolling it at its max speed (which would not be C unless it had no mass) would probably not work. If the sections of the bridge that collapse at the same time are 5 kilometers wide, it would be different than just 5 centimeters. You need more info! 😠

Originally posted by AThousandYoung
It'd become infinitely heavy and instantly smash the bridge.

I do believe you got that right.

If you have a ball go near the speed of light it will burn to plasma in a fraction of a second in the air above the bridge, so there is no problem here: The bridge will not collapse by the balls weight.

Even a more modest speed, that meteors posess entering the atmosphere (in the order of 30 km/sec), will burn it into ashes in a very short interval of time.

The bridge will not hold of a completely different reason.

Originally posted by FabianFnas
If you have a ball go near the speed of light it will burn to plasma in a fraction of a second in the air above the bridge, so there is no problem here: The bridge will not collapse by the balls weight.

Even a more modest speed, that meteors posess entering the atmosphere (in the order of 30 km/sec), will burn it into ashes in a very short interval of time.

The bridge will not hold of a completely different reason.

"Assume zero friction"

Originally posted by AThousandYoung
"Assume zero friction"

Then me might as well assume the speed of light. 😛

Originally posted by UzumakiAi
That's ridiclulous. You need more information. If it takes 500 years for one section to collapse, you could roll it at .000001 kph. It it takes 10^-100000000000000000000 nanoseconds to collapse, rolling it at its max speed (which would not be C unless it had no mass) would probably not work. If the sections of the bridge that collapse at the same time are 5 kilometers wide, it would be different than just 5 centimeters. You need more info! 😠

assume the bridge section the ball is on collapses instantaneously. That shoulda been obvious.

Originally posted by FabianFnas
Then me might as well assume the speed of light. 😛

most of these puzzlers assume things that don't happen in reality.

I've asked for the minimum speed, not the maximum speed.