Q1-Give reason of the following:
1-Icebergs floating in sea water are dangerous ships.
2-A submarine can float like an ordinary ship and sink when required.
3-A balloon filled with hydrogen or helium rises in the air.
4-An iron nail sinks in water but a huge ship made of iron and steel floats in water.
Q2-Answer the following question
1-The density of a substance is maximum in its solid states.intermediate in its liquid states and minimum in its gaseous state.Explain
2-Which two forces act on the object when it is immersed in a liquid? How does their magnitude determine that the object will float or sink in the liquid?
Guys help me tomorrow is my exam
Answers
Answer:
Q1 - (1) ICEBERGS are very dangerous for ship as ICEBERGS are hugs masses of ice with about 9/10 portion below water and only 1/10 portion of it above surface of water.
2) A submarine uses ballast tanks filled with compressed air and when needed the air is released and takes on water which increases the density making it sink but when the water is pushed out the sub’s density is decreased making it float.
3) When a ballon is filled with hydrogen gas the weight of the ballon is less than the weight of air displaced by the ballon. Due to this extra upthrust, the balloon rises up. But as it rises higher, the density of air decreases and upthrust becomes less and ultimately upthrust becomes equal to the weight of the balloon and it stops riding further.
4) the density of iron is more than the density of water therefore the weight of the nail is more than the upthrust experienced by it causing it to sink. However a ship although much larger than the nail floats because the ship is hollow from inside and this space is filled with air which reduces the average density of the ship lower than that of water. Thus even with a small portion of the ship submerged under water, the weight of the water displaced by it becomes equal to the weight of the entire ship.
Q2 -
1) The solid form of most substances is denser than the liquid phase so a block of most solids will sink in the liquid but a block of ice floats in liquid water because ice is less dense. Upon freezing the density of water decreases by about 9%. This is due to cooling of intermolecular vibrations allowing the molecules to form steady hydrogen bonds and locking into positions of hexagonal packing upon freezing to ice. These bonds are shorter in the crystal than in the liquid.
2)The two forces that act on the body are:
Downward direction - weight of the body
Upward direction - upthrust of the liquid
solution.