Newton's laws of motion -- Constaint motion

AI Thread Summary
The discussion revolves around solving a physics problem involving a massless pulley and a block on a frictionless surface. The user attempts to determine the acceleration of the block when a constant force P is applied to the pulley. Through the use of free body diagrams, it is clarified that the tension in the wire is related to the applied force, leading to the conclusion that P equals twice the tension (P = 2T). The final acceleration of the block is derived as P/2M, resolving the user's confusion. The interaction highlights the importance of free body diagrams in understanding the forces at play in such mechanics problems.
Vv anand
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Homework Statement


In the following diagram a massless pulley is pulled by a constant force of magnitude P. There is no friction between the block and the floor. The acceleration produced in the block if mass m is? PIC ATTACHED

Homework Equations


Took a1/2=a2 where a1 is accn of block and a2 is accn of pulley since a3 that is accn of the string attached to wall is 0

The Attempt at a Solution


tried solving by taking acceleration but found that pulley is massless so I'm pretty confused atm and pls help me and clear my doubt
 

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Answer is P/2M but i end up getting P/M
 
If P is the force pulling the pulley, what is the tension in the wire?
 
That is not given sir...and P is the force pulling pulley
Chestermiller said:
If P is the force pulling the pulley, what is the tension in the wire?
 
Vv anand said:
That is not given sir...and P is the force pulling pulley
Have you drawn a free body diagram of the pulley, or do you feel that you have advanced beyond the point where you need to use free body diagrams? From a free body diagram of the pulley, what are the three forces acting on the (massless) pulley?
 
Chestermiller said:
If P is the force pulling the pulley, what is the tension in the wire?
Yes sir P is the force on the pulley,
Tension is not given..I calculated it as MG as There does not exist any other force that exists on M (surface is frictionless)
 
Vv anand said:
Yes sir P is the force on the pulley,
Tension is not given..I calculated it as MG as There does not exist any other force that exists on M (surface is frictionless)
Chestermiller said:
Have you drawn a free body diagram of the pulley, or do you feel that you have advanced beyond the point where you need to use free body diagrams? From a free body diagram of the pulley, what are the three forces acting on the (massless) pulley?
I hv drawn it..just had the doubt that Is P=2T?
 
Vv anand said:
I hv drawn it..just had the doubt that Is P=2T?
Let's see your diagram.
 
Vv anand said:
Yes sir P is the force on the pulley,
Tension is not given..I calculated it as MG as There does not exist any other force that exists on M (surface is frictionless)
You don't think that the wire tension is acting on the mass?
 
  • #10
Chestermiller said:
Let's see your diagram.
Of course sir
 

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  • #11
Chestermiller said:
You don't think that the wire tension is acting on the mass?
Yes sir i just uploaded the fbd
 
  • #12
Is it correct...By doing this i get the answer
 
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  • #13
So, as you have found from your fbd, P=2T. So, ma=T=P/2
 
  • #14
Chestermiller said:
So, as you have found from your fbd, P=2T. So, ma=T=P/2
Wow!...I calculated it myself... Hats off to ur organization sir...Really obliged to get to know about ur organization ..Will surely recommend it to others
 
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