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by Ron Kurtus

A total of 94 comments and questions have been sent in. They are listed according to date.

List of next 10 letters




Floating Apply law to an experiment Philippines
Viscosity What is viscosity? Canada
General Many questions on fluids Philippines
Fluids Why does a metal ship float? Ghana
Fluids What is osmosis? Ghana
Floating Calculate the size of the boat Canada
Floating Will an object of a density of 3g/ml float.? USA
Floating Upward and downward force in water India
General Possible to drink a liquid in space by using straw? USA
Fluid Applications Can buoyancy move a propeller? Philippines

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First 10 letters

Apply law to an experiment

Topic: Floating


November 26, 2011

can i apply law on this experiment? then what law is that? and explain how can you say?

shella mai - Philippines



The ability to float is called Buoyancy. It follows Archimedes' principle that states that buoyancy equals the weight of the displaced fluid.

Check Experiments with Fluids for some ideas.

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What is viscosity?

Topic: Viscosity


November 7, 2011

What is viscosity,really? Please explain it with examples in terms of the particle theory. How does it relate to flowing of liquids? :)

Ashley - Canada



Viscosity is the resistant of a fluid to internal motion. It can be thought of the sliding of layers within the fluid. A good example is when you pour a liquid like water, which has a relatively low viscosity, compared with pouring thick oil, which has a relatively high viscosity. There is less internal resistance in water, so it flows much easier than the thick oil.

Viscosity is related to the size and molecular bonding of the substances molecules. At lower temperatures, molecular motion is slower and the viscosity of a fluid such as oil becomes greater.

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Many questions on fluids

Topic: General


July 2, 2011

1.Which is correct regarding fluid characteristics?
2.what influences the pressure indicated in the pressure gauge for example 200kg/cm2?
3.In an open loop hydraulic circuit pressure,where the relief valve is being installed?
4.In a hydraulic system with total displacement of 200Liters,how is the flow rate given?
5.In a hydraulic cylinder,what influences the velocity or the speed of piston to move? long it take to fill the cylinder displacement is 10liters,pump flow rate 20Ltrs/min?
7.What is not belong to hydraulic system,expansion valve,filter,limiting valve or cooler?
8.In hydraulic system what is being installed at the high pressure side?
9.It change the flow of hydraulic fluid from one to another direction?
10.It is an electro magnetic device which control the opening or closing of the fluid valve by,remote or automatic?
11.A hydraulic or pneumatic valve which has spring and ball with block flow and free flow fluid direction?
12.What will be the effect of dirty hydraulic cooler to the hydraulic system?
13.What is the effect of flow control valve if it is being installed in hydraulic system?
14.Hydraulic and pneumatic motor and cylinder is an example of?
15.What components is used to set the line pressure in a pneumatic circuit?
16.What symbols will indicate that the hydraulic pump,transformer,resistor and flow control valve is variable?
17.What is the device in an automated hydraulic system that control the final process?
18.What is the most common diagram using lines in presenting electrical circuit on the paper showing electrical symbol?
19.What is the unit in the hydraulic system composed of an electrical motor mostly hydraulic reciprocating pump that compressed hydraulic fluid to high pressure?

tnx,i hope you can help me..i'm waiting to your response.
have a nice day.

Jayvee - Philippines



I'm sorry, but that looks like a homework assignment. Also, there are just too many questions for us to delve into.

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Why does a metal ship float?

Topic: Fluids


February 18, 2011





See our lesson on How Objects Float in Fluids.

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What is osmosis?

Topic: Fluids


February 18, 2011

what is osmosis?




Osmosis is the tendency of a fluid, usually water, to pass through a porous or semipermeable membrane into a solution where the solvent concentration is higher.

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Calculate the size of the boat

Topic: Floating


January 7, 2011

hi i am entering a cardboard race in school and i was wondering how could i calculate the densaty of the boat with people in it. i want to know because i would like to caculate the percentage of the boat that will float so we can diterman the hight of the wall

kolten 12 years old

kolten - Canada



It is easiest to work with a rectangular boat. The volume of the boat is the area of the bottom (length times width) times the height.

Calculate the weight of the people to put in the boat plus the weight of the boat. Then compare with the density of water, which is 62 lb/ft^3 or 1 gm/cm^3 or 1000 kg/m^3.

To find the height of the side of the rectangular boat, first multiply the density of water times the bottom area of the boat. Make sure the units are the same. Then divide the weight by the product of the density x area. That should give you the minimum height of the side of the boat.

Best wishes in your cardboard boat race. Le me know how it turns out.

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Will an object of a density of 3g/ml float.?

Topic: Floating


September 12, 2010

An object of a density of 3g/ml will float.

kenneth - USA



Water has a density of 1 g/ml. Thus and object with a density of 3 g/ml would not float. It would have to have a density less than water.

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Upward and downward force in water

Topic: Floating


August 19, 2010

why upward force is equal to downward force in water?

sana - India



The downward force on an object in water is due to the weight of the water above it.

Force in a fluid is in all directions. The upward force on the bottom of the object is equal to the weight of the water at that depth plus the weight of the object.

If the weight of the object is less than water, the object will move upward and float.

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Possible to drink a liquid in space by using straw?

Topic: General


August 14, 2010

Is it possible to drink a liquid in space by using straw? Explain please.

Pallav - USA



Liquid is placed in a small sealed plastic bag with a straw sticking out one end. The astronaut then squeezes the bag to force the liquid into his or her mouth.

Water in a space capsule will form into floating bubbles or globules. A straw can be used to suck the liquid into the mouth, since there is air pressure in the space capsule. See:

Obviously, a straw could not be used in free space since the astronaut would have to be in a space suit.

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Can buoyancy move a propeller?

Topic: Fluid Applications


August 11, 2010

Can be the fluid in a tank or stagnant water can be used to rotate a propeller due to its bouyant force? In what way or principles derives this ideas? How can we design a propeller rotating/moving using the bouyant force?

Ricson - Philippines



Buoyant force is the upward force on an object that has less density that the fluid, such as water. Unless the fluid was moving, it cannot cause the propeller to turn.

However, if the propeller was on the bottom of an object that was moving upward in the water, due to it buoyancy, it might move because of the motion of the water.

If the water at the bottom of the tank was heated, such that it flowed to the top of the tank, it could cause a propeller to turn.

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