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Solids and Fluids. General Physics 1. States of matter. Solid Crystalline Amorphous Liquid Gas Plasma. Hooke’s Law. Quick Problem.
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Solids and Fluids General Physics 1
States of matter • Solid • Crystalline • Amorphous • Liquid • Gas • Plasma
Quick Problem • The Golden Gate Bridge weighs 419,800 Tons (m = 3.808x108 Kg) is suspended by 500 vertical cables. After the bridge was suspended, the longest of those cables was 500 ft long (152.4 m). The cables are made of steel (Y = 200.0x109 Pa) and have a diameter of 68.26 mm. What was the length of the longest cable before the bridge was hung on it?
4 Facts About Pressure • It increases with depth • It always acts perpendicular to the surface • Pressures cannot be added unless they have equal areas • A lack of pressure (ie. a vacuum) doesn’t do anything
Fundamentally floating Net Pressure x Area = Net force, called “The force of buoyancy”
Archimedes’ Principle • The force of buoyancy is equal to the weight of the fluid displaced.
Quick Problem • Captain Hook has purchased a nuclear powered submarine from Russia to conduct his anti-Pan activities. Note: Submarines sink by sucking seawater (ρ = 1025 Kg/m3)into their holding tanks. • When Hook’s new sub (m = 43000 Kg) is floating on the water (the holding tanks are empty), what is the force of buoyancy? • If only 1/5 of the sub exposed when it floats, what is the volume of the sub that is under water? • How big (Vholding tanks = ?) must the holding tanks be if Hook wants to accelerate down at 1 m/s2 (neglecting hydro-friction) while totally submerged.
Pascal’s Principle • Most fluids can be approximated as incompressible.
Quick Problem • If A1= 25 cm2, and A2= 2 m2, what must F1 be in order to hold the 650 Kg SUV? • How far must plunger 1 move in order to lift the SUV 7 feet?
Continuity Equation • The volumetric flow rate of a fluid remains constant, no matter the size of the pipe.
Bernoulli’s equation • As velocity of a fluid increases, pressure decreases. Left side equals the right side within a streamline
Quick Problem (9.55) • The inside radius of the large portion of the horizontal pipe are1.25cm. Water flows to the right at a rate of 1.80(10-4) m3/s. Determine the inside radius of the constriction.
Other Applications • Airplanes & Helicopters • Gophers • Shower curtains • Curve balls • Beach ball in a leaf blower • Many many others
Quick Problem (9.27) • The area of the piston in the master cylinder is 1.80 cm2 and that of the piston in the brake cylinder is 6.40 cm2. The coefficient of friction between the shoe and wheel drum is 0.50. If the wheel has a radius of 34.0 cm, determine the frictional torque about the axle when a force of 44 N is exerted on the brake pedal.
Quick Problem (9.40) • A light spring (k=160 N/m) rests vertically on the bottom of a large beaker of water. A 5.00 Kg block of wood (ρ=650 Kg/m3) is connected to the spring. What is the elongation of the spring at the equilibrium point?
Acknowledments • The Golden Gate Bridge figure came from Howarddigital.com. • All remaining figures (except ‘fundamentally floating’) came from Serway/ Vuille (your textbook).