yasin 8.0 flashcards

Viscosity

Viscosity

The resistance of a fluid to flow

Temperature Changes in Liquids

Temperature affects the viscosity of fluids. In liquids, as the temperature increases, the viscosity decreases. As the temperature decreases, the viscosity increases.

Temperature Changes in Gasses

When heat is added to gasses, the particles move faster and collide more often, resulting in greater resistance or friction. This means that as the temperature of a gas increases, the viscosity increases. As the temperature decreases, the viscosity decreases.

Friction

A force that works to slow down motion as a result of surfaces rubbing against each other.

Flow rate

A measure of the speed at which a fluid flows from one point to another. It is determined by measuring the amount of fluid that flows past a given point in a given time.

Density

The amount of mass contained in a given volume. It describes how closely packed together the particles are in a substance.

Density rules

• If the density of a substance is greater than the density of the fluid, the substance will sink.

• If the density of a substance is less than the density of the fluid, the substance will float.

• If the density of a substance is the same as the density of a fluid, the substance will "hover" in place.

Equation for Density

Density = Mass / Volume

Force

A push or a pull

Buoyance

The tendency of an object in a fluid to rise or sink due to density differences with its surroundings.

Buoyant force

The upward force exerted by a fluid.

An object will rise in a fluid when

The density of the object is less than the density of the fluid, and the buoyant force on the object is greater than the force of gravity on the object.

An object will sink in a fluid when

The density of the object is greater than the density of the fluid, and the buoyant force on the object is less than the force of gravity on the object.

An object will float in a fluid when

The density of the object is equal to the density of the fluid, and the buoyant force on the object is equal to the force of gravity on the object.

Archimedes' principle

The buoyant force on an object is equal to the weight of the fluid displaced by the object.

Applications of buoyancy

Hot air balloons, airships, research platforms, and the oil-filled organ above the skull of a sperm whale.

Plimsoll line

Shows how heavily a ship can be safely loaded in different water conditions.

Pressure

The amount of force applied to a given area

Changes in pressure

Air pressure changes with altitude. The layers of air in Earth's atmosphere extend more than 160 km above Earth's surface. Close to the surface, we experience air pressure as a result of all those air particles above us being pulled toward Earth by the force of gravity. There is less air pressure if we travel to higher altitudes because there are fewer layers of air above us, and the air there is less dense.

Pressure and depth

Pressure in a fluid also changes with its depth. For example, the weight of water in the upper part of a swimming pool presses down on the water in the lower part of the pool. The greater the depth of water, the greater the pressure at that point. This is why you feel greater pressure when swimming at the bottom of a pool than you do when swimming at the surface.

Pressure and fluid flow

If a fluid is allowed to move, it will always go from an area of higher pressure to an area of lower pressure. You make use of this property when you use a straw to drink from a juice box. Your mouth creates an area of lower pressure. The juice in the box is at a higher pressure, so it travels up the straw and into your mouth.

Pressure and temperature

The pressure exerted by a fluid is the sum of all the forces exerted by the individual particles in the fluid. When the temperature is increased, the particles move faster and strike the walls of the container more often and with more energy. At a constant volume, an increase in temperature results in an increase in pressure. If the volume of the container cannot increase, its pressure increases, possibly resulting in an explosion.

Compression

A decrease in volume caused by a force. If you kick a soccer ball, you force the air particles inside into a smaller volume. The shape of the ball changes temporarily because the air particles inside it are compressed.

Compressibility

The property of being able to be compressed.

Incompressible

Materials in a liquid state are said to be ___________, which means they cannot be compressed easily.