Add these two velocity vectors to find the magnitude of their resultant vector

4.6 m/s in the same direction as 5.8 m/s velocity.

Velocity is a vector quantity. It has both magnitude and direction.

Taking the 5.8 m/s  moving to the right as positive, then the 1.2 m/s moving to the left will be negative.  

∴ 5.8 + -1.2 = 5.8 - 1.2

                   = 4.6 m/s.

Since the answer is positive, it has the same direction 5.8 m/s velocity.

The resultant velocity vector is 4.6 m/s to the right.

f=ma newton

f=100x2.5=250n

conduction, convection, radiation