physics (sound)

• starmoonsun

  15 Jul 07, 18:13

  A scientist carry out an expt to determine the speed of sound in air by employing a friend to fire a cannon at a certain distance and then timing the interval between the sight of the smoke and the sound of the "boom".
  
  distanct is 500m and the time taken is 1.6s.
  
  If the speed of light is 300 000km/s and is taken into account. what will be the new speed of sound in air?
  
  the ans is 312.6m/s...
  
  im sorry! missed out a line =x
• tut4nkh4m3n

  15 Jul 07, 18:30

  o lvl standard? got this kinda question meh?
• Lexanez

  15 Jul 07, 19:57

  A level question?
  
  What values are given? How far is the scientist standing from his friend? How long before he heard the sound after the spark is seen?
• unclebutcher

  15 Jul 07, 20:04

  Originally posted by starmoonsun:

  A scientist carry out an expt to determine the speed of sound in air by employing a friend to fire a cannon at a certain distance and then timing the interval between the sight of the smoke and the sound of the "boom".
  
  If the speed of light is 300 000km/s and is taken into account. what will be the new speed of sound in air?
  
  the ans is 312.6m/s... but i dunno how to derive to this... can anyone help ?

  certain information is missing eg i think distance btw scientist and friend. pls write out the full question and i can help
• eagle

  19 Jul 07, 16:34

  Think the answer is not very accurate
  
  Speed of sound = Distance divided by time
  
  . = 500 / 1.6
  . = 312.5 m/s
• hisoka

  19 Jul 07, 16:39

  cannot be solved. we have no idea if the smoke is produced at the same time as the sound. even if we do, time we see smoke is affected by wind, temperature etc. when can we actually see the smoke?
  
  wheres the reaction time? there might be different time for different sensory inputs.
  
  
• unclebutcher

  19 Jul 07, 20:51

  Originally posted by starmoonsun:

  A scientist carry out an expt to determine the speed of sound in air by employing a friend to fire a cannon at a certain distance and then timing the interval between the sight of the smoke and the sound of the "boom".
  
  distanct is 500m and the time taken is 1.6s.
  
  If the speed of light is 300 000km/s and is taken into account. what will be the new speed of sound in air?
  
  the ans is 312.6m/s...
  
  im sorry! missed out a line =x

  assuming no reaction time
  
  300,000km/s = 300,000,000m/s
  
  500/300,000,000=1.67*10^-6 S for light to travel to scientist.
  
  500m/(1.6-0.00000167sec)=500m/(1.59999833)=312.500326m