Question

Two bodies of masses $m$ and $M$ are attached to the two ends of a light string passing over a fixed ideal pulley ($M>>m$). When the bodes are in motion, the tension in the string is approximately

• A. $(M-m)g$
• B. $mg$
• C. $2mg$
• D. $\left(m/M\right)mg$

Answer 1

The correct option is C $2mg$

$Mg-T=Ma$

$T-mg=ma$

Adding both equations

$(M-m)g=(M+m)a$

$\therefore a=\frac{(M-m)g}{M+m}\approx g[\because M>>m]$

$T-mg=mg$

$\therefore T=2mg$