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2012-08-01 06:10:02

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  1. what is the si system?
    Is the modern international system of units metric system
  2. what is the SI Unit for length?
  3. what is the SI unit for Mass?
  4. what is Density?
    density of a material is defined as its mass per unit volume.
  5. what is the unit for Density? What is its symbol?
    • The official symbol of density, after ISO recommendations, is the Greek letter 
    • ρ (pronounced rho and writed with italic font). Sometimes is used also d. 
  6. what is  the Density of water?
    1000 kg/m3
  7.  How much does 2.5 cubic metres of water weigh?
    2500 kg
  8. What is Relative Density and what is its unit?
    Relative Density is the ratio of the density of the object in consideration to the density of another object.
  9.  What is Specific Gravity and what is its unit?
    Specific Gravity is a unitless number (dimensionless quantity.) It is the ratio between the density of the material of interest and a standard material (e.g. water at it's greatest density). The units cancel out leaving a numerical value only. 
  10. . What is the SI unit for Time?
  11. 12. What is the SI unit for Temperature?
  12. 13.What is the relationship between Kelvin and Celsius?
    Degrees celsius is a scale based on the freezing and boiling point of water 0 and 100. Kelvin is a reflection of absolute temperatures. At absolute 0 equivalent to −273.15 °C. At this temperature there are no movements in all types of atoms.
  13. 14.What is a Centigrade?
    Centigrade(or degrees centigrade) is actually the unit for temperature measurement constructed by dividing the difference between freezing and boiling temperatures of water at atmospheric pressure in 100 divisions. 
  14.  Describe a situation where adding heat to a substance doesn't change its temperature?
    Turns to gas
  15. What is acceleration and what is its unit of measurement? How is it different to velocity?
    Velocity is the speed of an object in a given direction. 

    Acceleration is the rate of change of velocity.
  16. What is the commonly used value for gravity?
    in the SI (metric) system the official unit is metres/second/second or metres/(second squared)9.81 ms~2 (or 9.81 metres per second per second).
  17. 18.What are the 3 factors that affect pressure?
    • Pressure = 
    • Density x gravity x height
  18. Does the shape of a container affect the pressure at the bottom of the container?
    Oh yeah. Shape is everything. A sphere is the perfect shape for holding pressure. But the reason we dont see many spheres holding pressure is that they are also inconvenient in shape, so we have the next best thing - cylinders
  19. 20. Who is the unit of pressure named after?
    The pascal (symbol: Pa) is the SI derived unit of pressure, internal pressure, stress, Young's modulus and tensile strength, named after the French mathematician, physicist, inventor, writer, and philosopher Blaise Pascal
  20. 21. What formula would you use to calculate the pressure at the bottom of a tank?
    P = pxgxh
  21.  How many times bigger is a kilometre bigger than a millimetre?
  22. . What is the pressure at the bottom of a 2 metre swimming pool?
    • Pressure = Density x Gravity acceleration x Height 
    • Density of water = 1000 Kgm^-3 
    • Gravity acceleration = 9.8 ms^-2 
    • Height = 1.8 m 

    Pressure = 1000 x 9.8 x 1.8 = 17640 Pa