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: 
Recall Newton's Second Law,
*F=ma*

This means that resultant forces acting on an object will produce acceleration, which is a change in velocity. Remember that velocity is a vector, which includes both *speed* **and** *direction*. So if an object is accelerating, it has either its speed and/or direction of movement undergoing a change.

If an object is traveling at constant speed and still moving in the same direction, it is not experiencing acceleration, and thus the resultant forces acting on it are zero. This is exactly the same for an object at rest, except that its speed happens to be zero.
You might be confusing with pushing an object forward to maintain its motion.

For example, we pushed a CART forward and we got to maintain pushing it to keep it moving forever. Then, when we let go it will stop.

This is just because there is friction, this friction will cause the cart to stop, remove that and the cart will move forever! In real life Earth scenario however, this seldom happens, but push a cart in outer space and viola! It says goodbye us!