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Question:

Two masses m1=5 kg and m2=10 kg, connected by an inextensible string over a frictionless pulley, are moving as shown in the figure. The coefficient of friction of horizontal surface is 0.15. The minimum weight m that should be put on top of m2 to stop the motion is:

18.3 kg

27.3 kg

43.3 kg

10.3 kg

Solution:

from FBD of mass m1 we get T=5g
to stop the motion
T ≤ μ(m2+m)g
=> 5g ≤ 0.15(10+m)g
=> m ≥ 23.3 kg
so minimum mass that can stop motion is 23.3kg but among the options best option is option D.