Homework Help Forum: physics

Posted by Sasha on Monday, October 26, 2009 at 9:27pm.

When will your apparent weight be greatest, as measured by a a scale in a moving elevator; when the elevators: (a) accel. downward (b) accel. upward (c) is in free fall (d) moves upward at a constant speed? In what case would you weight be the least? When would it be the same as when you are on the ground?

• physics - bobpursley, Monday, October 26, 2009 at 9:42pm

  Think about it. weightapparent=mg+ma where a is up. What if a is down? What if a=-g?

  
  

• physics - MathMate, Monday, October 26, 2009 at 9:44pm

  Apparent weight = m(g+a) where g=9.8 m/s² a=acceleration, positive upwards. (a) W=m(g-|a|) (b) W=m(g+|a|) (c) W=m(g-|g|) = 0 (d) W=m(g+|0|) = mg

  
  

• physics - Sasha, Monday, October 26, 2009 at 9:47pm

  so the it would be the least on the way down, b/c your force, pushing on the scale is less. And it is greatest on the way up, since your force of push is stronger. And I would say in free fall it is the same as ground state?

  
  

• physics - MathMate, Monday, October 26, 2009 at 9:48pm

  Rethink free-fall.

  
  

• physics - Sasha, Monday, October 26, 2009 at 9:55pm

  ohh okay so the weight would be the same on the ground if its moving up at a constant speed?

  
  

• physics - MathMate, Monday, October 26, 2009 at 9:58pm

  Exactly. When it moves upwards (or downwards) at a uniform velocity, the reaction on the floor is the same as the weight. You have probably experienced this when you ride on an elevator.

  
  

• physics - Sasha, Monday, October 26, 2009 at 10:04pm

  sweet!! thank you =)

  
  

• physics - MathMate, Monday, October 26, 2009 at 10:07pm

  You're welcome!

  
  

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