 # Pressure clarified Pressure What affects the pressure of

• Slides: 19 Pressure clarified Pressure • What affects the pressure of a liquid? ▫ Gravity ▫ The density of the liquid ▫ The depth of the liquid Pressure • Remember when I told you that pressure increased when you went farther down in the water… Well how does pressure relate to depth if pressure is force divided by area… Pressure Equation Derived • • • P = F/A = force / area Force/area = weight/area Weight/area = weight density x volume/area = weight density x area x depth / area = weight density x depth ▫ THEREFORE: Pressure = weight density x depth **Weight density = density x gravity Buoyant Force and Archimedes Principle Buoyant Force • Upward force that the fluids exerts • Opposite to gravity • Recall that forces are greater at greater depth ▫ Thus, results from the difference of the upward and downward forces applied to a submerged object • Since the upward forces come from deeper in the liquid, the object is pushed up making is lighter Buoyant Force Bigger Buoyant force in deeper liquids Why do I feel lighter in water? • Because the buoyant force pushes up against gravity, making you seem lighter in water Which one is easier to pick up? Why?  Archimedes’ Principle • An immersed object is buoyed up by force equal to the weight of the fluid it displaced. Displaced Water • the amount of liquid pushed aside by a submerged object • volume of liquid displaced equals the volume of the submerged object • the depth of the liquid is increased by the submerged object because the liquid rises. Archimedes Principle Common language: The buoyant force of an object is equal to the weight of the displaced The weight of this volume is equal to the buoyant force.  Weight: Sink or Float • When the weight is less than the buoyant force, the object will… rise to the surface and floats • When the weight of a submerged object is greater than the buoyant force… it sinks See how the buoyant force works Object floats because the buoyant force is bigger than weight Sinks. Why?  Density: Sink or Float? • If the object is less dense than water… it floats • If the object is more dense than water… it sinks • If it has the same density as water, it doesn’t sink or float… like a fish 