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Question: Answered & Verified by Expert
A block A of mass m1 rests on a horizontal table. A light string connected to it passes over a frictionless pulley at the edge of table and from its other end another block B of mass m2 is suspended. The coefficient of kinetic friction between the block and the table is μk. When the block B is sliding on the table, the tension in string is:
PhysicsLaws of MotionNEETNEET 2015 (Phase 1)
Options:
  • A m2+μkm1gm1+m2
  • B m2-μkm1gm1+m2
  • C m1m21+μkgm1+m2 
  • D m1m21-μkgm1+m2 
Solution:
1570 Upvotes Verified Answer
The correct answer is: m1m21+μkgm1+m2 

From the figure,
\(\begin{aligned}
& m_2 g-T=m_2 a \ldots \text { (i) } \\
& T-\mu_k m_1 g=m_1 a \ldots \text { (ii) } \\
& \text {multiply eqn (i) with } \mathrm{m}_1 \text { and eqn (ii) with } \mathrm{m}_2 \\
& m_1 m_2 g-T m_1=m_1 m_2 a \ldots \text { (iii) } \\
& T m_2-\mu_k m_1 m_2 g=m_1 m_2 a \ldots \text { (iv) } \\
& \text{From eqn (iii) and (iv), we get,} \\
& m_1 m_2 g-T m_1=T m_2-\mu_k m_1 m_2 g \\
& m_1 m_2 g\left(1+\mu_k\right)=T\left(m_1+m_2\right) \\
& \therefore T=\frac{m_1 m_2 g\left(1+\mu_k\right)}{m_1+m_2}
\end{aligned}\)

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