Question

Question #b38a1

Answer 1

`144N`

Explanation:

Let magnitude of the force be `F`,
Using Newton's second law of motion we obtain constant acceleration `a` as

`F=ma`

Inserting given value
`F=16a`
`=>a=F/16ms^-2` ......(1)

Assuming that initially the body is at rest, final velocity `v` of body after `3s` can be calculated with the help of kinematic expression

`v=u+at`

Inserting given values and using equation (1) we get
`v=0+F/16xx3`
`=>v=(3F)/16ms^-1` .....(2)

Once the force is removed the body moves at a constant velocity for next `3s`. Distance `s` covered in time is

`s=vt`

Inserting given values and using equation (2) we get
`81=(3F)/16xx3`
`=>F/16=9`

Solving for force we get
`F=9xx16=144N`