Forces and Fluids

Pressure

100

What is the equation for pressure?

Pressure (in Pascals) = Force (in Newtons)/Area (in Meters Squared) P = F/A

200

-Pressure exerted by the atmosphere depends on the... -As you go higher in the atmosphere, pressure...

-thickness of the atmosphere. -decreases because there is less atmosphere above you.

300

The pressure applied by one object on another depends on:

-The weight (which is equivalent to the force) of the object applying the pressure. -The area of contact between the two objects.

400

The pressure on an object in a fluid is exerted from all directions at an angle...

perpendicular to all surfaces of the object.

500

Pressure on an object in a fluid increases with:

-The depth at which the object is placed in the fluid. The deeper the object is into the fluid the more pressure it experiences. -The density of the fluid.

Buoyancy

100

-Buoyant force experienced by an object changes with its __________ and ___________. -Buoyant force experienced by an object does not change with _____________.

- changes with weight and shape. - does not change with depth of the object in the fluid.

200

The buoyant force experienced by an object is equivalent to the weight of...

water it displaces. The buoyant force experienced by an object is equal to the weight of water it displaces and this applies whether it floats or sinks.

300

An object will sink until it displaces its full __________.

An object will sink until it displaces its full WEIGHT.

400

-If the density of an object is GREATER than the density of the fluid it is in, the object ___________ and its full ___________ is displaced but its full ______________ is NOT displaced. -If the density of an object is SMALLER than the density of the fluid it is in, the object ___________ and its full ___________ is displaced but its full ______________ is NOT displaced.

-If the density of an object is GREATER than the density of the fluid it is in, the object SINKS and its full VOLUME is displaced but its full WEIGHT is NOT displaced. -If the density of an object is SMALLER than the density of the fluid it is in, the object FLOATS and its full WEIGHT is displaced but its full VOLUME is NOT displaced.

500

-In order to help boats float, engineers increase __________ in order to decrease __________. -They also increase ________________ so that the effect of the buoyant force increases.

-In order to help boats float, engineers increase VOLUME in order to decrease DENSITY since the greater the volume the lower the density. -They also increase SURFACE AREA so that the effect of the buoyant force increases.

Work With Fluids

100

Force (in Newtons) = ...

Force (in Newtons) = Pressure (in Pascals) x Area (in Meters Squared).

200

If someone places an empty can on a table and blows to the right of the can, in which direction will the can move and why?

The can will move to the right because the pressure to the right of the can (where there is movement in the fluid/air) decreases and the pressure to the left of the can is greater since the air there is still/not moving. As a result, the greater pressure on the left pushes the can to the right.

300

What is a hydraulic system and how does it work?

A hydraulic system uses a fluid to increase an input force. For example, force is applied to a small piston inserted into a closed container that has an in-compressible fluid. This force increases the pressure everywhere in the fluid equally (due to Pascal's Principle). As a result, the force applied to the large piston on the other side of the system is greater than the initial force.

400

Explain how a chimney works using both density and Bernoulli's principle.

-The air in the room is colder than the air inside the chimney and colder air is more dense than hotter air. Since the cold air is more dense, it pushes the hot, less dense, air inside the chimney (and above the fire) out of the chimney. So, the smoke keeps moving out of the house and not into it. -According to Bernoulli's principle moving air above the chimney (outside the house) has less pressure than the air inside the chimney. So, the air inside the chimney which is at a greater pressure moves out of the chimney to where there is less pressure. This means that the smoke created by the fire inside the chimney keeps moving out of the house and not into it.

500

Explain the process that allows an airplane to fly: -The ___________ and/or ____________ of a plane pull it forward. -The ___________ of an airplane's wing allows it to deflect air moving above it ___________ at a __________ speed. -The ___________ speed of the air above the airplane's wing, results in ___________ pressure above the wing. -The _____________ force exerted by the airplane's wing onto the air results in a(n) _______________ force exerted by the air onto the airplane which produces ___________. -The pressure below the wing of an airplane is ______________ than the pressure above the wing.

Explain the process that allows an airplane to fly: -The JET ENGINE and/or PROPELLER of a plane pull it forward. -The SHAPE of an airplane's wing allows it to deflect air moving above it DOWNWARD at a GREATER speed. -The GREATER speed of the air above the airplane's wing, results in LOWER pressure above the wing. -The DOWNWARD force exerted by the airplane's wing onto the air results in a(n) UPWARD force exerted by the air onto the airplane which produces LIFT. -The pressure below the wing of an airplane is LOWER than the pressure above the wing and so the pressure below pushes the airplane up.

Definitions

100

Any substance that has no definite shape and has the ability to flow.

Fluid

200

Series of closed containers that when used can increase force.

Hydraulic System

300

mass divided by volume 

density 

400

Upward force that is exerted by a fluid on any object in the fluid.

buoyant force

500

Force per unit area that is applied on the surface of an object.

Pressure

Miscellaneous

100

What is used to measure atmospheric pressure?

A barometer.

200

What is Archimedes' principle?

According to Archimedes' principle, the buoyant force on an object is equal to the weight of the fluid it displaces.

300

What is Pascal's principle?

According to Pascal's principle, when a force is applied to a fluid in a closed container, the pressure in the fluid increases everywhere by the same amount.

400

What is Bernoulli's principle?

According to Bernoulli's principle, when the speed of a fluid increases, the pressure exerted by the fluid decreases.

500

What did Archimedes yell through the streets when he discovered his principle?

Eureka