Question

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

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

Answer 1

The correct option is A $3:1$

Tension in string when lift is moving up with acceleration upwards=$T_1=mg+ma$

$=9.8N+4.9N=14.7N$

Tension in string when lift is moving down with acceleration downward=$T_2=mg-ma$

$=9.8N-4.9N=4.9N$

Hence the ration of the two tensions=$\frac{T_1}{T_2}=\frac{14.7N}{4.9N}$

$=3$