Unit 3: Motion, Forces, & Energy

Chapter 11: Motion & Energy

Big Idea: If an object is less dense than a fluid, it will float in the fluid.

If an object is more dense than a fluid, it will sink in the fluid

Mrs. Lee - Ch 11 2

4 Sections

1. Pressure

2. Floating & Sinking

3. Pascal’s Principle

4. Bernoulli’s Principle

Mrs. Lee - Ch 11 3

Sec 1: Pressure

KEY CONCEPTS• The amount of pressure you exert depends

on the area over which you exert a force• Pressure = Force

Area• In a fluid, all of the forces exerted by the

individual particles combine to make up the pressure exerted by the fluid

Mrs. Lee - Ch 11 4

Sec 1: Pressure (cont’d)

• Atmospheric pressure decreases as your elevation increases

• Water pressure increases as depth increases

Mrs. Lee - Ch 11 5

Sec 1: Key Terms

• Pressure• Pascal• Fluid• Barometer

Mrs. Lee - Ch 11 6

Sec 2: Floating & Sinking

KEY CONCEPTS• Density = Mass

Volume• By comparing densities, you can predict whether

an object will float or sink in a fluid• The buoyant force acts in the direction opposite

to the force of gravity, so it makes an object feel lighter

Mrs. Lee - Ch 11 7

Sec 2: Key Terms

• Density• Buoyant force• Archimedes’ principle

Mrs. Lee - Ch 11 8

Sec 3: Pascal’s Principle

KEY CONCEPTS• When force is applied to a confined fluid, the

change in pressure is transmitted equally to all parts of the fluid

• A hydraulic system multiplies force by applying the force to a small surface area. The increase in pressure is then transmitted to another part of the confined fluid, which pushes on a larger surface area

Mrs. Lee - Ch 11 9

Sec 3: Key Terms

• Pascal’s principle• Hydraulic system

Mrs. Lee - Ch 11 10

Sec 4: Bernoulli’s Principle

KEY CONCEPTS• Bernoulli’s principle states that as the speed of a

moving fluid increases, the pressure exerted by the fluid decreases

• Bernoulli’s principle helps explain how planes fly. It also helps explain how an atomizer works, why smoke rises up a chimney, & how a flying disk glides through the air

Mrs. Lee - Ch 11 11

Sec 4: Key Terms

• Bernoulli’s principle• Lift