Q: A mass of 1 kg attached to one end of a string is first lifted up with an acceleration 4.9 m/s^{2} and then lowered with same acceleration. What is the ratio of tension in string in two cases.

Sol: When mass is lifted up with acceleration 4.9 m/s^{2}

T_{1} = m(g + a) = 1 (9.8 + 4.9) = 14.7 N

When mass is lowered with same acceleration

T_{2} = m(g – a) = 1 (9.8 â€“ 4.9) = 4.9 N

$\large \frac{T_1}{T_2} = \frac{14.7}{4.9} = 3:1 $