Fluids: Buoyancy & Density - Chapter 8

It's for Grade 8 fluids dummies.

Weight

the force of gravity acting up on an object

Mass

the amount of matter that makes up an object/substance

Volume

the amount of space an object or substance takes up.

Displace

to take place of

Ways to calculate volume

L x W x H

By displacement

Density

A measure of the mass per unit volume of a substance

2 things Density depends on

Tthe mass of particles and how tightly the particles are packed.

Since particles of solids are usually closer together than the particles of liquids, solids…

are often denser than liquids.

Characteristic Property

A property that makes a particular substance different from others.

What Temperature is pure water most dense at?

4 degrees C

The process of water particles when they cool:

Water particles move farther apart and the volume increases. The mass stays the same but the density decreases.

Buoyancy

upward force created by a fluid that opposes the weight of an object.

Positively buoyant

An object is positively buoyant if its density is less than the fluid its in.

Negatively buoyant

an object is negatively buoyant if its Density is more than the fluid its in.

Neutrally buoyant

An object is neutrally buoyant is the object doesn’t sink or float.

How does density affect the buoyancy of an object?

If an object is more dense it’ll be heavier and sink. If it’s less dense it’ll be lighter and float.

Archimedes’ Principle

is that the buoyant force Is equal to the weight of the displaced water.

If an objects weight is heavier than the weight of the water that’s displaced, the object will sink.

Yes

Ballast Tanks

Tanks under a boat that help keep water displaced and the boat buoyant.

Swim bladder

Helps a fish balance its buoyancy, by keeping air in or letting air out.