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    7). Two particles P and Q of masses 7kg and 2kg respectively are connected by a light inextensible string. Particle P rests on a smooth table. The string passes over a smooth pulley fixed at the edge of the table and Q is hanging freely. The system is released from rest. Find the acceleration of P.

    Not sure what to do, I tried using F=ma:

    2g-T = 2a\rightarrow (1)
    T=7a\rightarrow (2)
    (1)+(2)\rightarrow 2g = 9a
    a=2.12ms^{-2}

    The actual answer is 2.18 ms-2. What have I done wrong?
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    usually g has the value 9.8
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    (Original post by ViralRiver)
    7). Two particles P and Q of masses 7kg and 2kg respectively are connected by a light inextensible string. Particle P rests on a smooth table. The string passes over a smooth pulley fixed at the edge of the table and Q is hanging freely. The system is released from rest. Find the acceleration of P.

    Not sure what to do, I tried using F=ma:

    2g-T = 2a\rightarrow (1)
    T=7a\rightarrow (2)
    (1)+(2)\rightarrow 2g = 9a
    a=2.12ms^{-2}

    The actual answer is 2.18 ms-2. What have I done wrong?
    If  2g = 9a take  g=9.8 so

     19.6 / 9 = 2.1778\rightarrow 2.18 ms -2
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    Yes, I know that.

    2g = 9a
    a = \frac{2g}{9} = 2.18ms^{-2}

    EDIT: Oh I see what I did. I somehow couldn't read my calculator properly >.< xD .
 
 
 
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