Question: In my text book they said that:

> 
> 1. If no resultant force acts on an object, it will not accelerate; **it will remain at rest or it will** **continue to move at constant speed**
> 2. If an object is at rest or is moving at a constant speed in a straight line ,we can say that there is no resultant force on it.
> 
> 
> 

Now my question as it concentrates more on the first point.

How if the resultant forces or force are zero still the object moves at a constant speed and some times it does not move (or it is at rest as they say)?

Answer: 
A small and simple analogy to get the basic insight:

If each month, you spent as much as you earn, you will have constant savings.
If you started without savings, you will continue to have zero savings. 
If you started with \$1000, it will remain \$1000. In short: with net revenue zero, your savings are constant. Change revenue in force and savings in velocity, and you get what you need.
Basically, if no \*\*net \*\* force is acting on a body, it's acceleration is zero...

Now, acceleration is the change in velocity in unit time... 

So, if velocity is constant or zero, it's acceleration is zero...

Hope this helps!!!