How much weight to sink a block of ice ?
Discussion
Not quite. The calculation needs to account for the buoyancy of the lead, but close enough. Also depends on the temperature of the water in the pond.
Density of ice at 0 degrees is 916.2 kg/m^3
Density of water at 4 degrees is 1000 kg/m^3
Density of lead (varies with T) is 11 340 kg/m^3
To sink the "density" of the ice and lead has to exceed that of the water.
Mass of ice = Mi
Mass of lead = Ml
Volume of ice = Vi = Mi / 916.2
Volume of lead = Vl = Ml / 11 340
Density of ice and lead = (Mi + Ml) / (Mi / 916.2 + Ml / 11 340) > 1000
3 + Ml > 3000 / 916.2 + 1000 Ml / 11 340
Ml (1 - 1000 / 11 340) > 3000 / 916.2 - 3
Ml > 0.274 / 0.9118
Ml > 0.300 kg
(Quick check: density of ice is 90% that of water, so extra 10% mass needed = 0.3 kg)
Density of ice at 0 degrees is 916.2 kg/m^3
Density of water at 4 degrees is 1000 kg/m^3
Density of lead (varies with T) is 11 340 kg/m^3
To sink the "density" of the ice and lead has to exceed that of the water.
Mass of ice = Mi
Mass of lead = Ml
Volume of ice = Vi = Mi / 916.2
Volume of lead = Vl = Ml / 11 340
Density of ice and lead = (Mi + Ml) / (Mi / 916.2 + Ml / 11 340) > 1000
3 + Ml > 3000 / 916.2 + 1000 Ml / 11 340
Ml (1 - 1000 / 11 340) > 3000 / 916.2 - 3
Ml > 0.274 / 0.9118
Ml > 0.300 kg
(Quick check: density of ice is 90% that of water, so extra 10% mass needed = 0.3 kg)
Depends on the temperature of the ice and how much air is in it. Assuming it to be solid, once it has passed the threshold for buoyancy, it should sink all the way down. The density of ice is approximately 90% that of water, so a ballpark figure would be 10% of the weight would need to be added as ballast. Neglecting the volume of the lead, water purity etc. Shape of the ice and depth of the pond is irrelevant.
TL:DR; Approximately 300g of ballast.
TL:DR; Approximately 300g of ballast.
Is this trickier than it seems or am I over thinking it?
21.16 cc of lead weighing 240g will push the ice under but the lead will then lose 21.16g as it goes into the water. I think. So add that.But thats just under 2 more ccs of lead, displacing 1.86 more ccs of water resulting in 1.86g more lost weight.
So I'll guess 240+21.16+1.86 = 263.2g ish
21.16 cc of lead weighing 240g will push the ice under but the lead will then lose 21.16g as it goes into the water. I think. So add that.But thats just under 2 more ccs of lead, displacing 1.86 more ccs of water resulting in 1.86g more lost weight.
So I'll guess 240+21.16+1.86 = 263.2g ish
CoolHands said:
What does being cylindrical have to do with it?
Excellent username, given the topic in question 
For those that are wondering what it's all about.
I intend to freeze some blocks of 'rubby-dubby' or chum (fish guts trimmings and slops)
They'll be moulded in small buckets, with a volume of around 3 litres. I wanted to know what size of lead weight to throw into the mix when I'm freezing them to be guaranteed that the blocks will sink. The lead weight , frozen in the mix will have a loop of line on that I will clip through a carabiner and slide down the anchor rope when I'm fishing off my boat. As the ice melts, the rubby-dubby trail will drift down the tide and attract fish under the boat.
The lead weight will be retrieved when the anchor is eventually hauled.
Yes I realise that frozen fish entrails are not the same density as ice and that seawater is slightly more dense than freshwater, but from the calculations you've done for me I recon that a pound of lead (454g)in each block should do.
Which is good, because I already have a good number of 1lb weights to hand
Ilovejapcrap said:
I need to know
Why are you doing this ?
Anglers love to experiment. Why are you doing this ?
http://www.worldseafishing.com/forums/threads/rubb...
Halmyre said:
I think he's chopped his wife up into chunks and kept her in the freezer and now wants to dispose of the body parts in his (extra deep) fish pond. And all you 'helpful' suckerspeople are now accessories.
If he followed my advice the polar bear will have disposed of the evidence by now. Gassing Station | Science! | Top of Page | What's New | My Stuff