a carpenter of mass 50 kg is standing on a weighing machine placed in a lift of mass 20 kg.a light string is attached to the lift. the string passes over a smooth pulley and is attached to the lift and the other end is held by the carpenter.when carpenter keeps the lift moving upward with constant velocity, find-​1. reading of the weighing machine​2. net force on the man.​3. net force on the weighing machine.​4. tension of the string


Suppose T is the tension. Then weight on the weighing machine is m1g-T and now tension T is m2g+(m1g-T). Now equating We get 2T=m1g+m2g or T=m1+m2g2. Now putting the values we will get T=35g. So weight on wighing machine is 15kg. So net force on the man is m1g-T=15g. So the net force on the wighing machine is also same as net force on the man which is again 15g.

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Actually, I do agree to his answer... but, I think that the net force is as he soes not undergo any acceleration... u know, the II law...
Fnet ma... 
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same goes for the machiene
 
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