Question

what is the net force

Answer 1

Force and acceleration are connected through mass, or F = ma

Here you have:

14 = 1.5m so that m=14/1.5m/s^2

Then if you have a Force of 21 N

You get:

F = 9.33... * 1.5 = 13.999999995 or 14N

Answer 2

Using the most basic rule of motion, F=ma, we can solve this.

Force = mass × acceleration

Force = 14kg × 1.5$\frac{m}{s^{2}}$

Force = 21 N

The unit of force is N (newtons), or $\frac{kgm}{s^{2}}$. Since the mass was already in kg, we didn't have to do anything.