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    Two particles A and B of mass 5kg and 3 kg respectively are connected by a light inextensible string. Particle A lies on a rough horizontal table and the string passed over a small smooth pulley which is fixed at the edge of the table. Particle B hangs freely. The coefficient of friction between A and the table is 0.5. The system is released from rest. Find
    a) the acceleration of the system
    b) the tension in the string
    c) the magnitude of the force exerted on the pulley by the string

    Why is Pythagoras used for question c) ?
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    Assuming you can do part (b), you now know the tension in the string. I haven't done the question, so I'll make up an answer - let's suppose it is 10 N. If you were the pulley, what would you feel? You'd feel 10 N acting straight down on you (because of the tension in the part of the string connected to particle B), and 10 N sideways (because of the tension in the part of the string connected to particle A).

    How would you find the resultant of these two forces?
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    Pythagoras is used because the the tension exerted on the pulley points away from the pulley, one vertically and one horizontally and the resultant is the the force exerted on the pulley and the resultant would be the hypotenuse of the triangle.
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    Thank you so much
 
 
 
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