Floating an Upside Down Bucket: Water Displacement Explained

[mrmike]

hi, I am after some help from a person with a understanding of water displacement principles.
On a small scale- if an empty 5 LTR bucket is floated on a body of water, it will float, if the bucket is filled with water it sinks.
But if the empty bucket is place upside down, thus trapping a 5Ltr volume of air, the weight required to sink the bucket is more than the weight of the 5 Ltrs of water, is this true, and is there a formula for working out the volume of Air trapped and what weight is required to sink it?

 

[lpfr]

But if the empty bucket is place upside down, thus trapping a 5Ltr volume of air, the weight required to sink the bucket is more than the weight of the 5 Ltrs of water, is this true, and is there a formula for working out the volume of Air trapped and what weight is required to sink it?

No, the force is equal to the weight of 5 litters of water.