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Terry. This is doing my head in and I have to go out now...will revisit this thread tomorrow !

Ok, back to the water level in the bath. I used to sit at the back in maths and lark about more than I should have. So I take no responsibility for my next idea. Would the water level not have gone up as soon as it was placed onto the duck's back, even though it was not yet in the water? So, when the ring fell into the water the level wouldn't have changed. Maybe. I just know there's a wet blanket nearby who is about to tell me I should get out more.

There are three possible answers.

1. no change in level.
2. level rises.
3. level falls.

We are talking about what happens to the level once the metal ring has fallen in.

If the object is less dense than water (if it floats on water), it
displaces a weight of water equal to the weight of the object. If the
object sinks in water, it simply displaces a volume of water equal to the
volume of the object.

This is known as the Principle of Archimedes.

Ha,ha! This doesn't really answer your questionBUT when the ring pleced on the duck's back the additional amount of water displaced is equal to the WEIGHT of the ring but if the ring is just placed in the water and allowed to sink, the amount of water displaced is equal to the VOLUME of the ring. Methinks!

Can you figure out the difference in water level? i.e More or Less when on the duck's back than when in the water?

Just couldn't resist joining in - guastafeste - 'cos I don't have a rubber duck

Assuming....

1. The duck is lighter than the ring
2. Area of duck(with ring on)submerged is greater than the area of the ring

Then water level would fall as duck rises and ring drops?

Jolan,
That's it.

According to Archimedes’ principle, an object floats because it displaces an amount of water equal to the weight of the object. So to float when the weight is placed on it, the duck must displace a volume of water that equals the weight of the ring.

Since the metal ring is denser than water, the volume of the displaced water is greater than the volume of the ring. When the ring falls in the water and sinks, it displaces only its own volume of water.

The water level, then, drops.

Good on yeh, Ixion. I agree. My argument goes as follows.

When the ring is on the duck (which is floating), it displaces its weight in water.

When it is thrown in & sinks, it displaces its volume of water.

Since the rock weighs more than an equivalent volume of water, it is displacing more water when floating than when it is at the bottom of the bath. So when it is thrown in, the level of the bath water falls.

Crikey! Have we gone nuts? TTFN

Hi Terry!
Well put! I wuz writing as you were writing. Seems the problem is solved.

Have we gone nuts? Nuttier than a squirrel's turd I'd say.