newtonian mechanics - If something that is moving at constant velocity has no net force acting on it, how come it is able to move other objects?

Let's say 10 kg block is sliding on a frictionless surface at a constant velocity, thus its acceleration is 0.

According to Newton's second law of motion, the force acting on the block is 0:

$a = 0$

$F = ma$

$F=0$

So let's say that block slid into a motionless block on the same surface, the motionless block would move.

Wouldn't the first block need force to be able to move the initially motionless block? I understand that it has energy due its constant velocity, but wouldn't it be its force that causes the displacement?

Answer

Here's a slightly different but equivalent way to think about it.

Forces describe interactions between two objects. If two objects are interacting, they exert forces on each other. If two objects are not interacting, they do not exert forces on each other. Thus, an object doesn't "carry around" a force with it. A force is not a property of an object, just as dmckee explains. Instead, we describe interactions between two objects using the more-abstract concept of force.

In your block-hits-other-block scenario, it's tempting to ask where did the force come from if colliding object had $F_\text{net}=0$? But when forces are viewed as interactions, it becomes more apparent that the force didn't come from anywhere within one of the objects. There simply wasn't an interaction before they collided, so we wouldn't ascribe the existence of a force force.