Force and acceleration

  • Thread starter oooo
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Here is a problem from our freshman physics homework--it seemed pretty simple and self-explanatory:
(refering to a diagram) 22.5 newtons of force must be used to pull the 4 kg block across the rough surface at a constant velocity of 6.7 m/sec to the right. If the string pulling the block rightward were to break, what would be...
(a) the acceleration of the block:
Now, isn't the formula for acceleration a=F/m?
Wouldn't a = 22.5N/4kg = 5.625 m/s^2??? It seems simple enough, yet it is marked wrong. If I made a silly mistake, I would like to know why, because it seems really easy and I don't know where I went wrong.
THEN, after that, it prompts me to find the time it would take for the block to stop. Not quite sure how to figure that out... any suggestions?
 

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  • #2
Hootenanny
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oooo said:
Wouldn't a = 22.5N/4kg = 5.625 m/s^2???

Nope. What is the direction of the force acting relative to the velocity of the block?
HINT: You are very close.

~H
 
Last edited:
  • #3
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ooh, so it is -5.625! Thanks!
OH! and about my time question, I thought about it some more and I figured it out (no need to help) but thanks though!
 
  • #4
Hootenanny
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oooo said:
ooh, so it is -5.625! Thanks!

My pleasure.

~H
 

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