Science Grade 8 Ch. 4

Fluid

any substance that can flow and take the shape of the container that holds it.

gas

Is a fluid that fills the entire container no matter the size of the container

Pressure

is the amount of force per unit area applied to an object’s surface.

underwater pressure acting on a diver

The pressure on the diver will increase with depth. The pressure at the bottom (Buoyant Force) of the diver is greater than the pressure at the top because there would be more water underneath the diver than there would be about the diver.

depth

Pressure increases with depth.

density formula

Mass divided by volume. Pressure impacts this.

buoyant force

an upward force applied by a fluid on an object in the fluid.

buoyant force acting on a diver

The difference between the upward force from the pressure and the downward force from the pressure on each diver is the buoyant force on each diver.

Archimedes’ Principle

The weight of the fluid that an object displaces is equal to the buoyant force acting on the object.

know the details of the pic on pg 65

BALLOON: When pushing down on the balloon it is going to take more force to push it down because the weight of the water is greater than the weight of the balloon. The balloon has more buoyant force because more water has been displaced. BUOYANT FORCE: is pushing up on the balloon, tennis ball, and billiard ball.

significance of the smaller flasks

to show displacement

force acting on the objects

Buoyant Force. The larger the object, the greater the buoyant force acts on it.

why an object floats or sinks

FLOATS: When the weight of the water displaced by an object equals the weight of the object, the object floats.

SINKS: When the weight of an object is greater than the weight of the water displaced, the object sinks.

Pascal’s principle

When pressure is applied to a fluid is a closed container, the pressure increases by the same amount everywhere in the container.

how a piston works in a fluid

The output work is 2x the input work. Pushing on the piston increases the pressure equally throughout the fluid in the piston.

Bernoulli’s Principle

The pressure of a fluid decreases when the speed of that fluid increases.

relationship between speed and pressure in a pinched garden hose

The water speeds up in the pinched part of the hose. When speed increases, pressure decreases

drag force

A force that opposes the motion of an object through a fluid

factors that affect drag force

Size, Shape, Speed, Density.