Forces and Motion

Front

Fluid Noun

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[floo-id]

Back

Fluid

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A substance, such as a liquid or gas, that has no fixed shape and can flow easily when under pressure.

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Example: Gases and liquids are fluids because their particles can move freely, unlike the fixed particles in a solid, allowing them to flow and change shape.

Front

Pressure Noun

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[presh-er]

Back

Pressure

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The continuous physical force exerted on or against an object by something in contact with it, distributed over an area.

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Example: The weight of the column of air above you creates atmospheric pressure; this pressure is lower at high altitudes because there is less air above you.

Front

Pascal Noun

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[pas-kal]

Back

Pascal

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The standard international unit of pressure, equivalent to one newton of force applied over an area of one square meter.

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Example: Applying a small force to a fluid in a small area generates a much larger force in a larger area, because pressure is transmitted equally throughout the fluid.

Front

Hydraulic System Noun

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[hy-draw-lik sis-tuhm]

Back

Hydraulic System

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A mechanical system that uses pressurized fluid acting on pistons of different sizes to transmit and multiply a force.

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Example: This diagram shows how a small downward force on a small piston creates pressure in a fluid, which then exerts a large upward force on a larger piston.

Front

Pascal's Principle Noun

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[pas-kalz prin-suh-puhl]

Back

Pascal's Principle

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A principle stating that a pressure change at any point in a confined incompressible fluid is transmitted throughout the fluid.

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Example: Squeezing a container of liquid (applying external pressure) causes the pressure to increase equally everywhere inside, forcing the liquid out of all holes with the same force.

Front

Lift Noun

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[lift]

Back

Lift

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An upward force on an object that moves in a fluid, created by a pressure difference above and below it.

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Example: This diagram shows the four main forces acting on an airplane, with Lift being the upward force that counteracts the airplane's weight.

Front

Bernoulli's Principle Noun

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[ber-noo-leez prin-suh-puhl]

Back

Bernoulli's Principle

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A principle stating that an increase in the speed of a fluid occurs simultaneously with a decrease in its pressure.

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Example: This diagram shows air moving faster over the curved top of a wing, creating lower pressure, while slower air underneath creates higher pressure, resulting in an upward force called lift.

Front

Buoyancy Noun

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[boi-uhn-see]

Back

Buoyancy

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The ability or tendency of an object to float in a fluid, caused by an upward force the fluid exerts.

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Example: An upward force from the water, called the buoyant force, pushes on the boat, counteracting the downward force of the boat's weight, allowing it to float.

Front

Buoyant Force Noun

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[boi-uhnt fors]

Back

Buoyant Force

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The upward force exerted by a fluid that opposes the weight of a partially or fully immersed object.

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Example: An upward buoyant force from the water pushes on the boat, balancing the downward force of the boat's weight, which allows it to float.

Front

Archimedes' Principle Noun

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[ar-kuh-mee-deez prin-suh-puhl]

Back

Archimedes' Principle

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A principle stating that the buoyant force on a submerged object is equal to the weight of the fluid it displaces.

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Example: An object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces, as shown by the scales.