Other Effects of Fluids (Pascal’s Principal and Bernoulli's Principal) Chapter 4 Section 3 Other Effects of Fluids (Pascal’s Principal and Bernoulli's Principal)

I. Pascal’s Principle Pascal’s Principle- when pressure is applied to a fluid in a closed container, the pressure increases by the same amount everywhere in the container Observed with hydraulics (machines operated by fluid) B. Hydraulic Device- consists of two pistons (moving plunger), one at each end of a U-shaped tube.

I. Pascal’s Principle

I. Pascal’s Principle 1) System A – Full of fluid and press down on left piston. The increase in fluid pressure is transmitted to the right piston. a) Both pistons experience the same fluid pressure b) Because both pistons have the same surface area, they will experience the same force.

I. Pascal’s Principle 2) System B– The right piston has a greater surface area than the left. a) Area of the small piston is 1 cm² and the area of the large piston is 9 cm². b) The right piston has an area 9 times greater than the left piston. c) Push on the left piston, pressure is transmitted equally to the right. d) Because area of right piston is 9 times greater, force on the left is multiplied by 9

II. Hydraulic Systems Use Pascal’s Principle A. Changing piston area results in changed force Hydraulic system- liquids transmit pressure in a confined fluid. a) When force is applied to a small piston (small area) it is multiplied when acting on a larger piston (large area) at the other end b) increased pressure is transmitted through fluid, which pushes on a larger piston surface area same pressure over larger area results in more force.

II. Hydraulic Systems 2) Common hydraulic systems Hydraulic lifts hydraulic brakes 3) Hydraulics are Long Lasting- since they use fluids to transmit pressure, hydraulic systems have few moving parts that can jam, break, or wear down.

II. Hydraulic Lifts 4) Hydraulic lift Uses a) Mechanics raise cars b) Lift ladders on fire trucks c) Dump trucks d) Cranes

II. Hydraulic Brakes 5) Hydraulic Brakes a) Driver pushes on the pedal, which pushes on small piston b) The piston exerts pressure on the brake fluid c) Pressure is transmitted through fluid to larger pistons within the wheels d) Each these piston pushes on a brake pad e) System multiplies force with only a slight push allowing you to stop a large car

Hydraulic Brakes

III. Bernoulli’s Principle Fluid Motion- fluids naturally flows from an area of high pressure to an area of low pressure. Ex: Drinking from straw Air removed from straw, creating an area of low pressure Outside high pressure pushes down on the surface forcing the drink up B. Bernoulli’s Principle- pressure of a fluid decreases when the speed of that fluid increases.

III. Bernoulli’s Principle 1) Demonstration: a) Fill the bag b) Raise the paper c) Make the ping-pong ball float Explain how these demonstrations work 2) Bernoulli’s Principle- helps explain how planes fly, why smoke rises up a chimney, how roof can fly off in high winds, and how soccer ball curves.

III. Bernoulli’s Principle Objects Shape- Design can cause air to move at different speeds above and below object If air above object is faster this results in fluid pressure pushing object upward If the air moves faster below the object, fluid pressure pushes it downward.

III. Bernoulli’s Principle Airplane Flight- The wing of an airplane is designed to produce lift (an upward force). Because the wing is slanted, the air that hits it is forced downward as the plane moves. Air exerts an equal but opposite force on the wing and pushes it upward (Newton’s 3rd Law) This helps the plane take off

III. Bernoulli’s Principle Faster-moving air following the disk’s curved upper surface exerts less pressure than the slower-moving air beneath it Air flows over top and bottom in same amount of time, however the top has more distance for air to flow across, the air is actually moving faster Avg. Speed = Total Distance/Time

Objects In Flight

III. Bernoulli’s Principle Chimneys- smoke rises partly because hot air rises, and partly because it is pushed. 1) Wind blowing across the top of a chimney lowers the pressure. 2) Higher pressure at the bottom pushes air and smoke up the chimney.

Because air moves from areas of high to low pressure, the higher pressure on the left side of the soccer ball causes the ball to curve right.