Question

A mass of $1\,kg$ is suspended by means of a thread. The system is (i) lifted up with an acceleration of $4.9 \, m \, s^{- 2}$ (ii) lowered with an acceleration of $4.9 \, m \, s^{- 2}$ . What is the ratio of tension in the first and second case?

• A. $3:1$
• B. $1:2$
• C. $1:3$
• D. $2:1$

Answer 1

Answer: (A)

Case-I:

Using newton’s second law of motion,
$T_{1}- \, mg=ma$
$T_{1}=m \, \left(g + a\right)$
Case – II:

Using newton’s second law of motion
$mg-T_{2}=ma$
$T_{2}=m \, \left(g - a\right)$
From equation (i) and (ii)
$\frac{T_{1}}{T_{2}}=\frac{g + a}{g - a}=\frac{9.8 + 4.9}{9.8 - 4.9}=\frac{3}{1}$