Two masses connected via pulley: find acceleration

  • Thread starter pivoxa15
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  • #1
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Homework Statement


Two masses A and B, and of mass 1.6kg and 2.4kg respectively are connected by a light string which passes over a frictionless pulley. Calculate the acceleration of the 1.6kg mass.


Homework Equations





The Attempt at a Solution


To get started I must know whether the two masses both have the same acceleration. Is that true? I know the tension of the system is the same.

Assuming it's true I get a simultaneous equation that looks like
16-T=1.6a
24-T=2.4a

which works out for a=10m/s^2 and T=0 which is a bit fishy. But if a is different for each mass than there are 3 variables but only two equations.
 

Answers and Replies

  • #2
cristo
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The two masses have the same acceleration (they are connected by a string!) The smallest mass will move upwards, so its resultant force will be T-16, hence your first equation should read T-16=1.6a
 
  • #3
2,255
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I see. The system should have a predetermined positive, negative direction. It's not the case that upwards is always + and downwards always - in this pulley problem.
 

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