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Chapter 17.3. How do buoyancy and Archimedes’ principle relate to fluids?. Buoyancy. measure of the upward pressure a fluid exerts on an object. What is Archimedes’ principle?. the force exerted on an object in a liquid is equal to the weight of the fluid displaced by the object. Example.
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Chapter 17.3 • How do buoyancy and Archimedes’ principle relate to fluids?
Buoyancy • measure of the upward pressure a fluid exerts on an object.
What is Archimedes’ principle? • the force exerted on an object in a liquid is equal to the weight of the fluid displaced by the object.
Example • If a rock weighs 2.25 N using a spring scale is placed in water • the scale will then register 1.8 N • the water experts a force of 0.45 N
According to Archimedes’ principle the weight of the water displaced was 0.45 N
Why do objects sink and float? • If the buoyancy factor is greater than the weight of the object, the object floats. • If the buoyancy factor is less than the weight of the object, the object sinks.
Why does a block of steel sink, but a steel boat float? • 1 cubic meter of water = 9,800 N • 1 cubic meter of steel = 76,400 N • What happens?
The block of steel is flattened and hollowed inside to make a boat, approx. 10 cubic meters. • How much water is displaced? • 10 cubic meters of water = 98,000 N • 1 cubic meter of steel = 76,400 N • What happens?
Charles’ law • The volume of a gas increases with increasing temperature. • The volume of a gas decreases with decreasing temperature.
How does Charles’ Law explain how a hot air balloon works. • As the air inside is heated it will become less dense than that the air outside the balloon
What is atmospheric pressure? • the force required to hold the air around the earth • At the Earth’s surface the atmospheric pressure is 101,300 pascals or newtons.
Boyle’s Law states • 1. as the pressure of gas increases, its volume decreases proportionately. • 2. as the pressure of gas decreases, its volume increases proportionately.
Formula for Boyle’s law • P1 = initial pressure V1 = initial volume • P2 = new pressure V2 = new volume • P1 V1 = P2 V2
Example • Suppose 5 L of air at atmospheric pressure(101.3 Kilopascals) is compressed in a 0.5 L aerosol can. What is the pressure of the compressed air in the can? • Work the problem
HOMEWORK: • Compare and contrast Charles’s law and Boyle’s Law
Viscosity: • 1. Measure of a materials resistance to flow. • 2. Determined by the siae and shape of the molecules
Temperature and Viscosity • As a liquid gets warmer its viscosity decreases. • As a gas gets warmer its viscosity increases.
HOMEWORK: • P. 307 Problems 1-3 • Honors 1-5