Question

A bob of mass ${}^{\prime }{m}^{\prime }$ is attached to ceiling of a lift with the help of string as shown. Calculate tension in string when lift is accelerated up with acceleration ${}^{\prime }{a}^{\prime }$.

• A. $m(g+a)$
• B. $m(g-a)$
• C. $m\sqrt{g^2+a^2}$
• D. $mg$

Answer 1

The correct option is A $m(g+a)$

as acceleration is up,
In frame of reference of lift pseudo force acts downward . So, FBD is

where $ma$ is the pseudo force acting on the bob of mass $m$ which is creating tention in the string
$\Rightarrow T=m(g+a)$