Sinking block of wood?

Question

You're at the beach on vacation with your family. Your brother has a block of wood floating in a water-filled bucket. He says, "Hey, if I wanted this wood to sink into the water withough touching it, I could put this bucket in the hotel's elevator and press the button to go up, right?" Is he right or has he been out in the sun too long?

Answer 1

Out in the sun too long.

Answer 2

He is absolutely right. Due to inertia which the block of wood will experience more than the water molecules separately, the wood will sink.
But in a normal elevator, the effect will not be too great. To really notice the effect, the elevator should have a relatively high speed of acceleration while rising up.

Answer 3

He might be right not enough information provided to know for sure. For the this experiment the water can assumed to be incompressible so its density will not increase due to upward acceleration.

The missing information is the density of the block of wood and the vertical acceleration of the elevator. The downward force of the block would would be (g + acceleration) x mass of wood.

The flaw in the plan is as soon as the elevator reached top speed and stopped accelerating the wood would bob back up.

Answer 4

I am afraid that your brother is incorrect. the upward velocity or change in altitude would have zero effect upon the fact that the block of wood displaces more weight of water than the weight of the block. That is why the block floats.

Answer 5

Too much sun. From the general theory of relativity, being in a gravitational field is indistinguishable from being inside an accelerating object (e.i elevator that is speding up) . It floats.

Answer 6

Better sit him underneath a sunshade...poor lad! It might work if you tried it in a rocket! Though I doubt it as the water in the bucket would be forced down with the wood as well.