o lvl phy qns

• davidche

  4 Oct 07, 20:11

  
  
  1) A car is driving on a horizontal flat road with a constant speed.
  
  As the car moves uphills, the speed starts to slow down meaning the forces acting against the car increases(following me?)
  
  What force acting against the car actually increased?(material of the surface is the same)
  
  2) why does a coin and a feather fall at the same time in vaccuum?
  ( they are different mass right?)
  
• smartboy4

  4 Oct 07, 20:14

  Originally posted by davidche:

  1) A car is driving on a horizontal flat road with a constant speed.
  
  As the car moves uphills, the speed starts to slow down meaning the forces acting against the car increases(following me?)
  
  What force acting against the car actually increased?(material of the surface is the same)
  
  2) why does a coin and a feather fall at the same time in vaccuum?
  ( they are different mass right?)
  

  1) got such question asked meh? seems like talk about gravity
  
  2) no air resistance (this one u dont know how to take o level)
• hegu

  4 Oct 07, 20:17

  1) the component of weight against the direction of movement increase lor. when horizontal there is no component of weight along the direction of movement
  
  2) no air resistance hence both fall at same acceleration g=9.81
• omgukilledkenny

  4 Oct 07, 20:24

  Originally posted by hegu:

  1) the component of weight against the direction of movement increase lor. when horizontal there is no component of weight along the direction of movement
  
  2) no air resistance hence both fall at same acceleration g=9.81

  yea..
• wishboy

  4 Oct 07, 20:27

  Originally posted by omgukilledkenny:

  yea..

  \
  x2
• davidche

  4 Oct 07, 20:28

  Originally posted by hegu:

  1) the component of weight against the direction of movement increase lor. when horizontal there is no component of weight along the direction of movement
  
  2) no air resistance hence both fall at same acceleration g=9.81

  1) I understand now.
  can i ask how is this weight calculated? it shouldnt be 9.81 because the car isnt moving vertically uphills right?
  
  2) mass doesnt affect the acceleration?
• omgukilledkenny

  4 Oct 07, 20:30

  Originally posted by davidche:

  1) I understand now.
  can i ask how is this weight calculated? it shouldnt be 9.81 because the car isnt moving vertically uphills right?
  
  2) mass doesnt affect the acceleration?

  1) you gotta know the angle of the slope
• smartboy4

  4 Oct 07, 20:31

  2) even in normal air no vacuum, fall at different speed has nothing to do with mass, have to see the size of the surface against air resistance.
  
  
• Kuali Baba

  4 Oct 07, 20:34

  Originally posted by davidche:

  1) I understand now.
  can i ask how is this weight calculated? it shouldnt be 9.81 because the car isnt moving vertically uphills right?
  
  2) mass doesnt affect the acceleration?

  Use trigonometry to calculate the magnitude of the forces acting parallel to the direction of travel. You'll need the angle of the incline.
• davidche

  4 Oct 07, 20:49

  Originally posted by Kuali Baba:

  Use trigonometry to calculate the magnitude of the forces acting parallel to the direction of travel. You'll need the angle of the incline.

  thanks alot. I guess all i need to know now is that its the weight that adds on to the opposite force
• davidche

  4 Oct 07, 20:50

  Originally posted by omgukilledkenny:

  1) you gotta know the angle of the slope

  understand. It will get pretty complicated to calculate the weight.
  
  Thanks for the help!
• MyPillowTalks

  4 Oct 07, 21:52

  
  1) A car is driving on a horizontal flat road with a constant speed.
  
  As the car moves uphills, the speed starts to slow down meaning the forces acting against the car increases(following me?)
  
  What force acting against the car actually increased?(material of the surface is the same)
  
  Gravitational potention energy? The Ep=mgh, the newton's 2nd law, the gravity,is pulling the car down, thus resultant force= car puling torque - the pulling force down
  
  2) why does a coin and a feather fall at the same time in vaccuum?
  ( they are different mass right?)
  
  the freefall theory if i not wrong
• icyboiz

  4 Oct 07, 21:53

  YES YES THAT'S IT SO SMART OF U ALL
• eagle

  4 Oct 07, 22:24

  Originally posted by davidche:

  understand. It will get pretty complicated to calculate the weight.
  
  Thanks for the help!

  wrong
  
  it's extremely standard if you draw the diagram properly
  
  just remember all forces can be resolved into 2 other forces, which can be further broken down again (but don't do this)
  
  This is the main property of vectors
• purpledragon84

  4 Oct 07, 23:52

  
  
  when it was on a horizontal road, only got air resistance.. but go up the slope, mg sin theta pulling car backwards.. so car slow down..
• davidche

  5 Oct 07, 11:05

  Originally posted by purpledragon84:

  when it was on a horizontal road, only got air resistance.. but go up the slope, mg sin theta pulling car backwards.. so car slow down..

  understood, and sounds quite logical too. Thx!!