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Final velocity of a ball pushed by compressed airpls. help

  • #1
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final velocity of a ball pushed by compressed air..pls. help!!

Homework Statement


Compressed air is used to fire a 1.72 kg ball vertically upward from a 1.50 m long
tube. The air exerts a upward force of 28.7 N on the ball as long as it is in the tube.
With what velocity does the ball leave the top of the tube?


Homework Equations


F=ma
V12 = v02+2ad


The Attempt at a Solution


so i used the given mass and force to get an acceleration. then using the acceleration i plugged it in to the second equation assuming vinitial to be zero and my asnwer is coming out wrong can someone point me in the right direction thanx :))
 

Answers and Replies

  • #2
rock.freak667
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Resultant force= Upward force-downward force

what's the downward force in this case?
 
  • #3
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wld the downward force be the friction..but there is no mention of any friction in the question
 
  • #4
rock.freak667
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wld the downward force be the friction..but there is no mention of any friction in the question
if you throw a ball upwards, it does not continue to go upwards, what makes it fall back to earth? (it has a mass m and is under the influence of gravity g)
 
  • #5
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ok but that tells us what happens after it is released they're asking for velocity just before it's released from the cannon/tube
 
  • #6
rock.freak667
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ok but that tells us what happens after it is released they're asking for velocity just before it's released from the cannon/tube
When you find the resultant force, you can get the resultant acceleration...:wink:

and in the formula [itex]v_1^2=v_0^2+2ad[/itex]

what do you need to find to get the value for v1?
 
  • #7
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we have the distance(1.50) and we now have an acceleration but would vinitial still be equal to zero??
 
  • #8
rock.freak667
Homework Helper
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we have the distance(1.50) and we now have an acceleration but would vinitial still be equal to zero??
Yes it would be safe to assume the initial velocity as zero.
 
  • #9
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thank you so much :))
 

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