One sphere is standing, another is flying with AddForce.

There’s a ray between them. I wonder how to instantiate objects on that ray with a specific distance?

Vector math is your friend. Given the two sphere position vectors movingSphere and stationarySphere…

```
// get the direction by subtracting, and normalizing so it has a length of 1
Vector3 direction = (movingSphere - stationarySphere).normalized;
// create your objects - this will create 10 of them, but I assume you'll want to do something
// to stop creating them if you reach the moving sphere or something
float separationDistance = 2; // units of separation
for (int i = 0; i < 10; i++)
{
float distance = (i + 1) * separationDistance;
Vector3 objectPosition = stationarySphere + (direction * distance);
// TODO : instantiate your object at objectPosition
}
```

Something like that should give you the basic idea. The key is finding a unit vector that points in the right direction, then multiplying it by the distance along the ray to find the new position.