Ca 1 physics

• Work done by a constant force


  1. The product of the component of the force parallel to the displacement times the displacement of a body

  2. The Scalar (dot) product between force and displacement of a body
• W


  Fs cos θ
• Work


  • Scalar quantity
  • Unit: (kgms) or J (1Nm)
• Joule


  The work done by a force of 1N which results in a displacement of 1m in the direction of the force
• No work done if there is no movement or the force is perpendicular to the displacement
• Work


  • Positive - has a component in the direction of motion
  • Zero - has no component in the direction of motion
  • Negative - has a component in the opposite direction
• Energy And conservation of energy 


  The system's ability to do work. Scalar quantity
• Kinetic energy


  Energy associated with the motion of body
• Potential Energy


  Energy stored in a body or system because of its position, shape and state in a gravitational field
• Elastic Potential Energy


  Energy stored in a compressed or stretched spring
• Spring constant


  The constant K of a spring (unit = N/m)
• Average force on the spring


  F =1\2 kx^2
• Within Elastic Limit, beyond those limits the spring may deform
• Power


  The rate at which work is done or energy is transferred
• Principle of conservation of energy: in an isolated system, total energy of that system is constant. Initial of total energy = final of total energy
• Instantaneous power


  The instantaneous rate of doing work
• Work-energy theorem: Work done by net force on a body = change in body's total energy
• Mechanical efficiency


  A measure of the performance of a machine, engine etc. defined as the ratio of the useful (output) work done to the energy input
• Chemical energy


  Energy released when chemical bonds between atoms and molecules are broken
• Electrical energy


  Energy that is associated with the flow of electrical charge
• Heat


  Energy that flows from one place to another as a result of temperature difference
• Internal energy


  Total of kinetic and potential energy of atoms or molecules within a body
• Fluid


  Any material that is unable to withstand a shear stress, responds with an irrecoverable flow
• Fluids


  • Useful in physics as liquids are incompressible
• Density


  Mass of substance divided by the volume
• Density of water = (1000kg/m3)
• Weight


  Can be found as mg=pVg
• Pascal


  Unit of pressure, N/m2
• Atmospheric Pressure


  1.01 x 10^5 N/m2
• Hydrostatic pressure


  Pressure exerted by a fluid at rest
• Fluid

  • Exerts pressure in all directions
  • Exerts pressure perpendicular to any surface it compacts
• Pressure


  Affected by the depth of the object
• Factors affecting pressure

  • Weight of the object
  • Force of the atmosphere pressing down
  • Force of the water pressing up
• Pressure


  P = Po + pgh, where Po is the initial pressure, p is the density, g is gravity, and h is the depth below the surface
• Absolute pressure


  The initial pressure or the difference in the initial and absolute pressure
• Gauge pressure


  The change in pressure, may or may not be atmospheric pressure
• Pascal's Principle


  When pressure is applied to an enclosed fluid, the pressure is transmitted equally to every point in the fluid and to every point on the walls of the container
• Buoyant force


  Force that buoys an object upward when it is immersed in a fluid
• Archimedes' Principle


  An object is buoyed up by a force equal to the weight of the fluid displaced
• Buoyant Force


  FB = ρVg, where ρ is the density of the fluid and V is the volume of the object