JEE MAIN - Physics (2002 - No. 60)

A light string passing over a smooth light pulley connects two blocks of masses $${m_1}$$ and $${m_2}$$ (vertically). If the acceleration of the system is $$g/8$$, then the ratio of the masses is
$$8:1$$
$$9:7$$
$$4:3$$
$$5:3$$

Explanation

AIEEE 2002 Physics - Laws of Motion Question 131 English Explanation
Assume that, mass m1 is greater than mass m2, so the heavier mass m1 is accelerating downward and the lighter mass m2 is accelerating upwards.

For mass $${m_1}$$ the equation will be

$${m_1}$$$$g-T=$$$${m_1}$$$$a$$

For mass $${m_2}$$ the equation will be

$$T-$$$${m_2}$$$$g=$$$${m_2}$$$$a$$

Adding those equations we get

$$a = {{\left( {{m_1} - {m_2}} \right)g} \over {{m_1} + {m_2}}}$$

$$\therefore$$ $${g \over 8} = {{\left( {{m_1} - {m_2}} \right)g} \over {{m_1} + {m_2}}}$$

$$ \Rightarrow {1 \over 8} = {{{{{m_1}} \over {{m_2}}} - 1} \over {{{{m_1}} \over {{m_2}}} + 1}}$$

$$ \Rightarrow$$ $${{{m_1}} \over {{m_2}}} + 1 =$$ $${8\left( {{{{m_1}} \over {{m_2}}} - 1} \right)}$$

$$ \Rightarrow$$ $${{{m_1}} \over {{m_2}}} = {9 \over 7}$$

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