Science physic

• fat_boy@87

  29 Oct 07, 18:42

  i need some help thanks
  
  1)explain why the pressure of air trapped in a close cylinder increases when the surrounding temperature increase
  
  2)given that the refractive index of diamond is 2.4 if the speed of light in a vacuum is 3 x (10 to the power of 8m/s) calculate the speed of light in the diamond
  
  3)a car of mass 500kg is being towed along a straight road so that it's velocity changes uniformly from 10m/s to 20m/s in a time of 8 seconds.during this time the frictional resistance is constant and equals to 500N
  
  1Q)what is the force exerted on the car by the towing vehicle
  
  2Q)when the speed of 20m/s is reached ,the towing force is reduced so that the car now moves with constant velocity.what is the resultant force on the car now
  
  3Q)what is the towing force
• absol

  29 Oct 07, 18:54

  1) when surrounding temperature increases, the air molecues in the closed cylinder gains energy and so moves faster. this increases their rate of collision with the walls of the cylinder and so increases pressure.
  
  2) do by this formula refractive index = spd of light in vacuum/spd of light in diamond. though i assume ur "3 x (10 to the power of Coolm/s" is 3/10^8m, spd of light in vacuum.
  
  3)1Q) acceleration = change in velo/time = 10/8 = 1.25 m/s^2
  Force exerted on car by towing vehicle = frictional force + (500)(1.25)
  = 500 + 625
  =1125N
  
  actually not really sure whether to add frictional force...
  
  2Q) constant velo = 0 accel
  
  if a=0, den F = (500)(0)= 0N
  so resultant is 0N.
  
  3Q) towing force when the car moving at const velo is the frictional force, 500N.
  
• fat_boy@87

  29 Oct 07, 19:06

  Originally posted by absol:

  1) when surrounding temperature increases, the air molecues in the closed cylinder gains energy and so moves faster. this increases their rate of collision with the walls of the cylinder and so increases pressure.
  
  2) do by this formula refractive index = spd of light in vacuum/spd of light in diamond. though i assume ur "3 x (10 to the power of Coolm/s" is 3/10^8m, spd of light in vacuum.
  
  3)1Q) acceleration = change in velo/time = 10/8 = 1.25 m/s^2
  Force exerted on car by towing vehicle = frictional force + (500)(1.25)
  = 500 + 625
  =1125N
  
  actually not really sure whether to add frictional force...
  
  2Q) constant velo = 0 accel
  
  if a=0, den F = (500)(0)= 0N
  so resultant is 0N.
  
  3Q) towing force when the car moving at const velo is the frictional force, 500N.
  

  btw i change Q2 liao a error occur nvm
  err for Q2 must i use sin
  and for Q 3 can explain why u use 500N X 1.25
• wishboy

  29 Oct 07, 19:55

  3)a car of mass 500kg is being towed along a straight road so that it's velocity changes uniformly from 10m/s to 20m/s in a time of 8 seconds.during this time the frictional resistance is constant and equals to 500N
  
  What is the towing force?
  
  Ans:
  
  F = ma
  
  a = (v-u)/t
  = (20-10)/8
  = 1.25 m/s²
  
  F = 500 kg * 1.25 m/s²
  = 625 N
  
  Total towing force = 625 + 500 = 1125 N
• absol

  30 Oct 07, 22:08

  500*1.25 is to find out the force needed to tow the car of mass 500kg at an acceleration of 1.25m/s^2, using the formula F = ma
• absol

  30 Oct 07, 22:15

  2)given that the refractive index of diamond is 2.4 if the speed of light in a vacuum is 3 x (10 to the power of 8m/s) calculate the speed of light in the diamond
  
  u use n = sin i/sin r only when u have either incidence angle or refracted angle on an object eg a ray is shining on the diamond.
  
  however in this question u do not have any light ray shining on the object...
  
  so theres the other formula u can use to find refractive index, n = speed of light in vacuum/ speed of light in object(in this case, the diamond)
  
  so jus sub in values into the equation above and do.
• hisoka

  30 Oct 07, 22:18

  Originally posted by fat_boy@87:

  i need some help thanks
  
  1)explain why the pressure of air trapped in a close cylinder increases when the surrounding temperature increase
  
  2)given that the refractive index of diamond is 2.4 if the speed of light in a vacuum is 3 x (10 to the power of 8m/s) calculate the speed of light in the diamond
  
  3)a car of mass 500kg is being towed along a straight road so that it's velocity changes uniformly from 10m/s to 20m/s in a time of 8 seconds.during this time the frictional resistance is constant and equals to 500N
  
  1Q)what is the force exerted on the car by the towing vehicle
  
  2Q)when the speed of 20m/s is reached ,the towing force is reduced so that the car now moves with constant velocity.what is the resultant force on the car now
  
  3Q)what is the towing force

  for 1: cos the textbook and the scientists say so