A box of mass 10 kg is lowered with a downward acceleration `4 m//s^(2)` . In the box there is a spring whose lower end is fixed to the box and a ball of mass kg is kept on its loose end, as shown below. At a certain instant when the spring (spring constant `= 100 N//m`) is found to be compressed by `5 cm`, tension in the cable `T` is :

Options

A. `65N`
B. `61N`
C. `60N`
D. `100N`

Answer

A

Explanation

A box of ……………..

`FBD` of the box is shown above. Writing Newton's second law.
`105 - T = 10(4)`
`T = 65 N`