Fluids under pressure Forces Anything that causes a

Fluids under pressure

Forces • Anything that causes a change in the motion of an object. • A push or pull.

Balanced forces: • Are equal in strength • Are opposite in direction • No movement

Unbalanced forces: • Are unequal in strength • Cause a change in speed or direction

Mass vs. Weight MASS WEIGHT • Stays the same anywhere in the universe • Kilograms (kg) • A measure of the pull of gravity acting on an object. • Newton (N)

PRESSURE • The force acting on a certain area of surface. • The larger the force, the greater the pressure. • The smaller the area, the greater the pressure.

Think about it What puts more pressure on your paper, writing with a dull pencil or a sharp pencil? Why?

Compression • Is a decrease in volume caused by a force.

PHASES OF MATTER • SOLID • LIQUID • Holds shapes • Shape of container • Fixed Volume • GAS • Shape of Container • Volume of Container

Compressing • Which takes the most effort to compress? • Which takes the least effort to compress? • Why do you not want to heat compressed gasses? • What is deformation in solids?

Compressed vs Uncompressed

Why do you not want to heat compressed gasses? • Gas molecules hit the walls of the container • Each hit is a small force • When you heat compressed gasses, there are more hits more forces more pressure inside the container than outside • EXPLOSION!!!

Implosion vs Explosion

• IMPLOSION occurs when the pressure is lower inside than outside • EXPLOSION occurs when the pressure is lower outside than inside

Think of the pop can experiment • When you boil water the vapour pressure of the water is equal to the pressure due to the weight of the atmosphere • When you put the can in the cold water, the water vapour condenses, and the pressure decreases • WHY?

Why do you not want to heat compressed gasses? • When you cool gasses, there are fewer hits less forces less pressure inside the container than outside • IMPLOSION!!!

CALCULATING PRESSURE • The unit for pressure is the Pascal (Pa) • You can determine pressure if you know the force and the area

Pressure • Formula: Pressure (P) = Force (F) Area (A) P A

SAMPLE PROBLEM 1 • An aquarium is filled with water that weighs 10 000 N. If the base of the aquarium has an area of 1. 6 m², what pressure does the water exert on its base?

SAMPLE PROBLEM 1 • An aquarium is filled with water that weighs 10 000 N. If the base of the aquarium has an area of 1. 6 m², what pressure does the water exert on its base? Force = 10 000 N Area = 1. 6 m 2

Problem 1 Solution P A

Problem 1 Solution P = F A P= 10 000 N 1. 6 m² P = 6250 Pa P A

SAMPLE PROBLEM 2 • If the atmospheric pressure is 101 200 Pa and you are holding your hand, the atmosphere is exerting a force on your hand. If the area of your palm is 0. 006 m², calculate the force on your hand.

Problem 2 Solution F=Px. A F = 101 200 Pa 0. 006 m² F = 607 N P A

SAMPLE PROBLEM 3 • The weight of water in a glass is 4. 9 N. If the water is exerting a pressure of 1700 Pa on the bottom of the glass, what is the area of the bottom of the glass?

Problem 3 Solution A=F÷P A = 4. 9 N 1700 Pa A = 0. 003 m² P A

Assignment • Complete the practice problems