The coefficient of friction between two surfaces is $\mu = 0.8$.The tension in the string shown in the figure is ........ $N$
A$0$
B$6$
C$4$
D$8$
Medium
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A$0$
a Maximum frictional force acting on the block $f=\mu m g \cos 30^{\circ}$ $f=0.8 \times 1 \times 9.8 \times 0.866=6.8 N$
Downward force $=m g \sin 30=1 \times 9.8 \times 0.5=4.9 \mathrm{N}$
since downward force is less than maximum frictional force, thus the tension in the string is zero.
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