physics chapter 1

• a physical quantity is a quantity that can be measured.
• A derived quantity is given by the multiplication or division of two or more base quantities. (can be calculated from a formula) 

  Eg: speed, area, volume
• base quantities!! ( SI unit, symbol for SI unit)

  • length ( metre, m )
  • mass ( kilogram, kg )
  • time ( second, s )
  • electric current ( ampere, A )
  • thermodynamic temperature ( kelvin, K )
  • amount of substance. ( mole, mol )
• prefixes!! ( factor 10 power, prefix, symbol)

  • 1012 Tera- T
  • 109 giga- G
  • 106 mega- M
  • 103 kilo- k
  • 10-1 deci- d
  • 10-2 centi- c
  • 10-3  milli- m
  • 10-6 mega- μ
  • 10-9  nano- n
• The precision of an instrument is the smallest unit that the instrument can measure.
• Avoid parallax errors: Position your eyes such that your line of sight is perpendicular to the  instrument
• Reduce random error: Repeat the measurement and take the average value of the measurements.
• instruments: measuring range, smallest division, example of usag.

  • measuring tape, zero to several metres, 0.1cm or 1mm, a persons waist
  • digital calipers, zero to 15cm, 0.01cm or 0.1mm, diameter of test tube
  • digital micrometre screw gauge , zero to 2.5cm, 0.001cm or 0.01mm, diameter or wire.
  • metre rule, zero to one metre, 0.1cm or 1mm, height of table
• how does digital caliper measure stuff?

  inside jaws: measure internal  diameter of object 

  outside jaws: measure external diameter of object.

  locking screw: ensures that the jaws dont move

  tail: measure depth of object

  zero button: reset the displayed length back to zero
• how does digital micrometre screw gauge measure stuff?

  anvil and spindle measures the diameter of the object.

  digital display. used to show the numerical value of the object

  zero button, reset the value to zero

  ratchet, can be turned so that spindle is in contact with the object.
• Period, T is the time taken for the pendulum to complete one oscillation
• simple pendulum is not affected by 

  o mass of bob 

  o amplitude of oscillation (angle of oscillation)
• Period of a simple pendulum is affected by  

  • length of the pendulum
• scalar quantities are physical quantities that have only magnitude.

  vector quantities are physical quantities that have magnitude and direction
• scalar:

  • distance
  • speed
  • mass
  • energy
  • time
• vector:

  • displacement
  • velocity
  • acceleration
  • force
  • weight
• speed is distance moved per unit time
• velocity is rate of changeof displacement
• formula:

  speed= distance/time taken

  velocity= displacement/ time taken