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Work and mass

  • Thread starter n124122
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  • #1
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Homework Statement


Is the amount of work depending on the mass?

Homework Equations


W=F*s
F=m*a

The Attempt at a Solution


attempt one:
because if you have a higher mass, it takes longer to make a certain object move over a certain distance, but it doesn't matter because time isn't measured. For example move a 4kg block over 3 meters with 6 newton or move a 20 kg block over 3 meters with 6 newtons, the work remains the same (3*6=18J).
Attempt two:
But when the mass is increased, in the formula F=m*a, the force is increased. So the work in the situation above should be increased? thereby making the work (20/4=5) 5 times bigger. What am i doing wrong?
 

Answers and Replies

  • #2
Doc Al
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attempt one:
because if you have a higher mass, it takes longer to make a certain object move over a certain distance, but it doesn't matter because time isn't measured. For example move a 4kg block over 3 meters with 6 newton or move a 20 kg block over 3 meters with 6 newtons, the work remains the same (3*6=18J).
Good. As long as the force and the displacement are the same, the work done will be the same.

Attempt two:
But when the mass is increased, in the formula F=m*a, the force is increased. So the work in the situation above should be increased? thereby making the work (20/4=5) 5 times bigger. What am i doing wrong?
In the above, the applied force is kept the same. So when the mass is increased, the acceleration is decreased. But so what?
 
  • #3
18
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Good. As long as the force and the displacement are the same, the work done will be the same.


In the above, the applied force is kept the same. So when the mass is increased, the acceleration is decreased. But so what?
thank you very much
 

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