Question

Question #9e417

Answer 1

`6s`

Explanation:

Using Newton's Second law of Motion
`F=ma`
Solving for acceleration and inserting given values we get
`a=F/m`
`=>a=-50/20=-2.5ms^-2`
`-ve` sign indicates that it is a retarding force.

Now using the kinematic equation
`v=u+at`
`0=15-2.5t`
`=>t=15/2.5=6s`