Chapter 13: Liquid Flashcards
The force per unit area that one object exerts on another
Depends on area over which force is distributed
Depends on area over which force is distributed, large area and small area have both
1) Smaller force
2) Larger force
Two blocks have the same weight, but the rightmost block exerts more
Pressure on the table
When you stand on one foot instead of two, the force you exert on the floor is
The same
When you stand on one foot instead of two, the pressure you exert on the floor is
More
Pressure
Force per unit area that a liquid exerts on an object
The liquid exerts a pressure on the bottom area of
The container
Depth dependent and not the volume
Dependent
Swim twice as deep, then twice as much weight of water above you produces
Twice as much pressure on you
Each layer holds the weight of the previous layers
Ex:
1) 2nd layer holds the weight of the 1st layer
2) 3rd layer holds the weight of the 1st and 2nd layer
Pressure in a liquid, the depth of the container was
Significant (depth matter)
Independent of shape of container, whatever the shape of the container, pressure at any particular depth is
The same
Acts equally in all directions, force pressing against a surface add up to a
Net force perpendicular to the surface
Water pressure provided by a water tower is
Greater if the tower is taller
Buoyancy
Apparent loss of weight of a submerged object, amount equals the weight of water displace
Displacement rule
A completely submerged object always displaces a volume of liquid equal to its own volume
Buoyant force
Net upward force that a fluid exerts on an immersed object is equal to weight of water displaced
The difference in the upward and downward forces acting on a submerged block is
The same at any depth
Whether an object sinks or floats (or does neither), depends on
Both buoyant force (up) and weight (down)
Density fluids will exert a
Greater buoyant force on a body than less dense fluids of the same volume
The reason a person find it easier to float in salt water compared with fresh water is because
The buoyant force on a given volume is greater in salt water than in fresh water
Archimedes’s Principle
An immersed body (completely or partially) is buoyed up by a force equal to the weight of the fluid it displaces
The principle relates buoyanacy to
Displaced liquid and applies to gases and liquids (fluids)
Depends on how the buoyant force compares with the object’s weight depends on
The object’s density
1) An object more dense than the fluid in which it is immersed will sink
Pob0 > pl
2) An object less dense than the fluid in which it is immersed will float
Pob0 < pl
3) An object that has a density equal to the density of the fluid in which it is immersed will neither sink nor float
Pob0 = pl
Whether an object floats or sinks depends upon the
1) Volume of the object
2) Volume of the fluid displaced
An object floats on the surface of a liquid if
The weight of object equals the buoyant force exerted by the fluid and the object’s weight equals the weight of the displaced fluid
Principle of floatation
A floating object displaces a weight of a fluid equal to its own weight
The same 1 ton of iron in a bowl shape displaces
A greater volume of water and the greater buoyant force allows it to float
Principle of flotation
A floating object displaces a weight of fluid equal to its own weight
As you sit in class, is there a buoyant force acting on you?
Yes, due to the displacement air
Every ship must be designed to
Displace a weight of fluid equal to its own weight
A change in pressure at any point in an enclosed fluid at rest is
Transmitted undiminished to all points in the fluid
The force exerted on the left piston increases the pressure in
The liquid and is transmitted to the right piston and applies to all fluids, gases and liquids
Pascal’s Principle like simple machines are three steps
1) Energy not multiplied
2) Pressure not multiplied
3) Only force
Pascal’s principle applies in
Hydraulic press and the pressure applied to the left piston is transmitted to the right piston
Pascal’s Principle application for gases and liquids
1) Seen in hydraulic devices and used in construction
2) In auto lifts at service stations
3) Increased air pressure produced by an air compressor is transmitted through the air to the liquid surface in an underground reservoir
4) The liquid transmits the pressure to the piston, which lifts the car
Surface tension is caused by
Molecular attractions
Beneath the surface, each molecule is
Attached in every direction by neighboring molecules
A molecule on the surface of a liquid is pulled only by
Neighbors on each sides and downward from below; there is no pull upward
These molecular attraction tend to pull the molecule from
The surface to the liquid causing surface tension
Surface tension is
Contractive
Factors affecting surface tension are:
1) The type of liquid
2) What is mixed with the liquid
3) Temperature of the liquid
1) The type of liquid
Water has greater surface tension than oil
2) What is mixed with the liquid
Soapy water has lower surface tension than water without soap
3) Temperature of the liquid
The molecule in a hot liquid have higher energy and are not bound tightly as in a cooler liquid
Drops of any kind are spherical because their surfaces tend to
Contract and force each drop into the shape having the least surface area for a given volume and to a sphere
The rise of a liquid in a fine, hollow tube or in a narrow space is called
Capillarity
Adhesion between the molecules of the glass and water draws
The film of water into the tube
Surface tension causes
The film on the surface to contract
This raises the liquid from below to
Rise into the tube
When the force of the surface tension balances out the weight of the liquid, so the liquid is
Stop rising
The height of rise depends upon
The weight of the liquid and the narrowness of the tube
The lighter the liquid, the
Higher the capillary rise
The narrower the tube, the
Higher the capillary rise
