gravity ..ice...and wood

[ermintrude35]

my 11 year old daughter has sience homework...I am clueless when it comes to sience...

...a block of wood and a block of ice , both weighing the same , are dropped from equal distances, why does the ice always land first?...the words "friction" and "gravity" are to be used in the answer..

.many thanks for any help ..

[gen2]

Wood is less dense than ice. The block of wood will therefore be larger than a block of the same weight of ice. The wood will therefore have a larger surface area than the ice. When dropped, gravity will act on each of them equally. Air friction (air resistance) will slow each of them down. The one with the larger surface area will experience more friction and will be slowed down more. The wood therefore hits the ground after the ice.

[jake-the-peg]

I suspect gen that the fact that ice has been chosen for the question is because ice is "slippery-er" than wood and experiences less friction as it falls through the air.

What you say is true and the fact that they say the blocks weigh the same makes me think they want both observations in an ideal answer.

Of course to be extra "smart" you could point out that the wood of some trees such as Holly or Lignum Vitae is denser than water (and hence ice) and could they please be more specific next time :c)

[Hamish]

It would also depend on the shape of the wood and ice blocks.

[Bert]

Ermintrude is also clueless when it comes to spelling "science". But what sort of daft question has her daughter been asked? What is the significance of the word "always"? In a proper scientific experiment, if the block of ice lands first once, it will always land first, given that the starting conditions are the same every time. And did Galileo waste his time dropping different lumps of metal off the Leaning Tower of Pisa? All objects (ice or wood) will fall at the same speed, apart from a tiny effect due to air friction, and the actual buoyancy of the object in the air. You would need a pretty good set-up to show that ice lands first. It would certainly not be perceptible to the human eye, if the objects are dropped from "reasonable" heights where terminal velocities do not enter into the problem.