Question

Forces F1(east) and F2 are simultaneously applied to a 3kg mass. When F2 is east, a=5m/s

Answer 1

Given:

$m=3\:\rm kg$

$a=5\:\rm m/s^2$

The net force applied to the mass

$$F=ma=3\:\rm kg*5\: m/s^2=15\: N$$