ISCI 2002 Exam 2

Pregunta	Respuesta
Density=	Mass/Volume
Density	-Important property of matter (solids, liquids, gases) -Measure of compactness of how much mass an object occupies -"lightness" or "heaviness" of materials of the same size
Density Example:	The density of mercury is 13.6 g/cm^3, so mercury has 13.6 times as much mass as an equal volume of water (density 1 g/cm^3).
Density of Water	1 g/cm^3
Volume=	Mass/Density
Mass=	Density x Volume
Pressure	Force per unit area that one object exerts on another
Pressure=	Force/Area
Pressure	-Depends on area over which force is distributed -Units in lb/ft^2, N/m^2, or Pa (Pascals)
Water Tower	Force of gravity acting on the water in a tall tower produces pressure in pipes below that supply homes
When an ice cube in a glass of water melts, the water level	remains the same
Buoyancy in a Liquid	Buoyancy- apparent loss of weight of a submerged object -amount equals the weight of water displaced
Archimede's Principle	-discovered by Greek scientist Archimedes -relates buoyancy to displaced liquid -states that an immersed body (completely or partially) is buoyed up by a force equal to the weight of the fluid it displaces
Apparent weight of a submerged object	weight out of water - buoyant force
If a 3-kg block submerged in water apparently "weighs" 1kg, then the buyoant force or weight of water displaced is 2kg	Buoyant Force= weight out of water - apparent weight. 3kg - 1kg= 2kg
Bouyant force is greater on an empty steel barge when it is:	floating on the surface
Buoyant force is greater on a submarine when it is:	submerged
What is the weight of water displaced by a 100-ton floating ship?	100 tons
Displacement rule:	A completely submerged object always displaces a volume of liquid equal to its own volume
Place a stone in a container that is brim-full of water, and the amount of water overflow equals the volume of the stone	*
Buoyant force is equal to the weight of fluid displaced	*
Understood by pressure differences	greater pressure against the box- Pressure on the top of box
Principle of flotation	A floating object displaces a weight of fluid equal to its own weight
The reason a person finds it easier to float in salt water, compared with fresh water, is that in salt water:	a smaller volume of water is displaced
Buyoyant force-	the upward force resulting from an object being wholly or partially immersed in a fluid
The Archimede's Principle-	An object immersed in a fluid experiences a buoyant force equal to the weight of the volume of fluid displaced
Both liquids and gases are considered fluids	*
Objects float in fluids because an upward force acting on it is greater than the downward force of its weight	*
An object will float in a fluid if its average density is less than the density of the fluid	*
An object will sink if its average density is greater than the density of the fluid	*
An object will be in equilibrium at any submerged depth in a fluid if the average density of the object and the density of the fluid are equal	*
When an object floats, some of it is submerged, displacing enough volume so that the buoyant force equals the weight force	*
A fish normally displaces its own:	volume of water, and weight of water
Ships float because the average density of the ship is less than the water it would displace	*
Oil floats on water,	since oil is less dense than water
Cream floats on milk,	since cream is less dense than milk
By taking in, or pumping out water, submarines can vary their buoyancy.	*
Is there a buoyant force acting on your classmates at this moment?	Yes, but it is insignificant compared with their weights

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