Steel Ball vs Steel and Mercury

How would a steel ball filled with mercury - no bubbles - act in a pinball machine?

Originally posted by AThousandYoung
How would a steel ball filled with mercury - no bubbles - act in a pinball machine?

If you take two eggs, one hard boiled and one not cooked, try spinning them. The hard boiled egg will spin but the one not cooked will refuse to spin due to internal friction of the liquid. I suspect there would be a similar reaction to your ball. It would probably not even roll at the same speed as a solid metal ball, would probably be sluggish in its roll so might not even activate those sensors based on the rubber string where it hits and a solenoid strikes it to send it elsewhere.

sounds about right, apart from not activating the sensors, as long as the ball has enough velocity then the force is the same.

you'd lose the stability of a spinning sphere so the path it travels would not be as straight.

interesting question 🙂

Originally posted by mortisdead
sounds about right, apart from not activating the sensors, as long as the ball has enough velocity then the force is the same.

you'd lose the stability of a spinning sphere so the path it travels would not be as straight.

interesting question 🙂

You probably have seen how fast those balls are going when they hit the sensor/barrier/kicker mechanism. If there was mercury inside, it might not go fast enough to trigger them.

I guess the pressure needed could be made less or more though.

Originally posted by sonhouse
You probably have seen how fast those balls are going when they hit the sensor/barrier/kicker mechanism. If there was mercury inside, it might not go fast enough to trigger them.

I guess the pressure needed could be made less or more though.

According to Newton the speed does not determine the force, the accelleration does.

Just trying to sound smart 😛

Originally posted by TheMaster37
According to Newton the speed does not determine the force, the accelleration does.

Just trying to sound smart 😛

Yes there is the old standard F=MA and such but we are talking about kinetic energy, Ke=MV^2 here. There has to be a certain amount of kinetic energy to activate the sensor, like those kid's clicker toys where you flex this curved metal piece and it takes a certain amount of flexing to make it click, anything less and nothing happens.

Originally posted by sonhouse
Yes there is the old standard F=MA and such but we are talking about kinetic energy, Ke=MV^2 here. There has to be a certain amount of kinetic energy to activate the sensor, like those kid's clicker toys where you flex this curved metal piece and it takes a certain amount of flexing to make it click, anything less and nothing happens.

SO we lose x amount of energy due to the inertia of the mercury, we lose y amount of stability (can we quantify this?) and the end product is a ball with y speed with the energy reduced by the inertia so less likely to interact with sensors but if you hit it hard enough it will be enough for the first few bounces, assuming that it can be aimed because of y.

Now, given that I am hopelessly addicted to Excel and simulation software, someone else will have to sit down and think about how to model all this, assuming that they want to figure it out 😉

As a random aside, Earth is full of liquid but it's spin means that instability from the liquids inertia is cancelled out, and we're in a stable orbit. Does that invalidate everything said so far or do we [simply, right?] need to include an s factor too?

What about a lead ball?

marginally softer so greater deformation, but also denser so more energy; will they balance out? perhaps yes, perhaps no.

Originally posted by mortisdead
marginally softer so greater deformation, but also denser so more energy; will they balance out? perhaps yes, perhaps no.

less energy I'd say ...

assuming the force from the flipper is constant the lead ball will have a smaller velocity than the steel ball (in ratio to relative densities)

the velocity squared element of the balls' KE will mean the stell ball has more energy.

(I think ...) 😕

Originally posted by wolfgang59
less energy I'd say ...

assuming the force from the flipper is constant the lead ball will have a smaller velocity than the steel ball (in ratio to relative densities)

the velocity squared element of the balls' KE will mean the stell ball has more energy.

(I think ...) 😕

So can we chart the basics of a steel ball filled with mercury on Excel, where you take a basically frictionless surface, say optically smooth glass flat and take a all steel ball and tip one end of the surface to cause a ramp.

Then find out what it the minimum angle it takes to get the steel ball rolling Vs the same thing with the steel ball now filled with mercury. My guess is the ramp angle would have to be somewhat higher to get it to start rolling and the velocity of the two if launched side by side would be different, the steel ball winning that race.

Like the guy says, the steel ball then might have more KE. Depends on just how much faster it goes than the mercury filled version. If the same ball was filled with lead instead of mercury, there would be no internal friction so it would end up with the exact same velocity as the all steel version and thus would always have a higher KE than the steel ball.


That kind of test would give some information about a pinball machine which has a surface angled down so the ball will roll to the front if the velocity is zero at some point. The exact angle I don't know, just that it is a ramp. 5 degrees? Not sure.

It would depend on the Thickness of the Wall of the Steel that housed the Mercury , then the fact that there were no bubbles ( Meaning No air ) would negate the effects of friction or countermovement of the mercury because there wouldn't be any room for movement . Therefore , the total mass of the two separate but solidly linked metals , would be equated as 1 thing , then Mass . Velocity . would be the only considerations , as that effective Hardness would still be basically the same ( Unless the wall thickness was very thin , then deformation would be possible)

Originally posted by sonhouse
If you take two eggs, one hard boiled and one not cooked, try spinning them. The hard boiled egg will spin but the one not cooked will refuse to spin due to internal friction of the liquid. I suspect there would be a similar reaction to your ball. It would probably not even roll at the same speed as a solid metal ball, would probably be sluggish in its roll ...[text shortened]... sensors based on the rubber string where it hits and a solenoid strikes it to send it elsewhere.

Ah, but an egg is not a sphere, the egg has much more resistance with the liquid inside.

Take a round bottle, roll it on it's side. Now take it and spin it end to end. The resistance of the liquid is much more end to end as opposed to rolling it on it's round side.

I have a boccie ball set, plastic with water inside. It's not much different than a wooden or metal set I've used before.

P-