a 11 kg mass is moving at 4.9 m/s what is the magnitude of the net force needed to stop this mass at 9.3 seconds

Heya!!

For this, let's start calculating aceleration magnitude with formula:

                                                  Δ   Being   Δ

                                              V = Final velocity

                                              Vi = Initial velocity

                                              t  = time

                                              a = Aceleration

⇒ Let's replace according the formula:

⇒ Resolving:

Now, we have the aceleration, so lets applicate second law of Newton for calculate net force applicated:

                                                  Δ   Being   Δ

                                                  F = Force

                                                  m = mass

                                                a = Aceleration

⇒ Let's replace according the formula:

⇒ Resolving:

Result:

The net force applicated is of -4,73 Newtons.

Extra:

The minus represents when the force acts in the opposite direction to the acceleration of the body.

Good Luck!!