PHYS 210 Other, Spring 2008

Physics210 revision for quiz 1 Things to memorize:   Unit of a force: 1Kg . m / s2 = 1 N=1 Newton     work exerted by spring (Hooke’s law)  and  If there is a force of friction acting, we can extend the work-kinetic energy theorem as:  Average power  Instantaneous power but  GPE:  Work done on the system equal to the change in the gravitational potential energy.  Conservation of mechanical energy   Changes in Mechanical Energy for Non-conservative Forces  density:  pressure: Fluid assumed at rest exerts a force perpendicular to a surface in contact with it if pressure varies over the surface , if P is the same over the surface  Pressure as a function of height (static fluid)  pressure difference between two levels in a fluid:  Pascal’s law: Pressure applied to an enclosed incompressible fluid is transmitted undiminished to all parts of the fluid. This is independent of the shape of the vessel  pressure of the atmosphere as a function of the height The pressure decreases exponentially with the height  Barometer: in vacuum  If p0= 1.013x105 pa then  Open-Tube Manometer:   Archimedes Principle: If a body, completely or partially immersed in a fluid, the fluid exerts an upward buoyant force equal to the weight of the fluid displaced by the body.  Buoyancy:  Two cases to be considered: a. Totally submerged body  b. Floating: In case of floating  The buoyant force is exerted by the fluid. It is influenced by the amount of fluid displaced by the object, not by its density.  Motion of sub immersed body in a fluid is determined by the densities of the object and fluid  Force on dam:   Net Work:  Change in kinetic energy:  Change in potential energy:  Work-Energy Theorem:  Bernoulli’s Equation:  This equation indicates that: 1. The pressure of the fluid decreases as the speed of the fluid increases. 2. The pressure of the fluid decreases with increasing elevation. Therefore you need a water pump in your apartment in a high floor  Torricelli’s Law: An enclosed tank containing a liquid of density has a hole at a distance y1 from its bottom. The hole is open to atmosphere (p1=p0) and A1 much smaller than A2. Suppose the air above the liquid is p (at level 2 in the Figure). Determine the speed of the liquid through the hole when the liquid level is h above the hole. Solution: A2 large means velocity is very small there : v2=0. Now apply Bernoulli’s equation: =>  Using Bernoulli's equation: P1 + (1/2) r v12 = P2 + (1/2) r v22 But A1 v1 = A2 v2 =>  Definition of the surface tension:  Given: mass of the strider m=2x10-5 Kg, radius of his foot assumed circular: r=1.5x10-4 m What is then the angle q, if the strider does not sink?