once we generate our loads what causes them to move around our system and the answer here is physics if i play my model we're going to run a complicated physics simulation that's analyzing the forces on each of the objects and the coefficients of friction between them and calculating where they should move to so in this case we've got a conveyor with a belt that's moving and that belt's got a friction coefficient and as the load is generated it's been dragged by the belt and accelerated before it ends up flying into space and gravity pulls it down to impact with the floor in the visualization tab we can turn on the physics view you can also use f8 on your keyboard to see this in a little bit more detail if i reset the model and use my step functionality to slowly see what happens you can see that a load is generated slightly above the surface of our conveyor and if we step forward a small fraction so it falls and lands on the conveyor we can see contact points between our load and the surface and these blue lines are showing the force of gravity pulling our load into contact with our conveyor and applying a force and these yellow lines are showing the force of friction because our belt surface is moving and we have a coefficient of friction set up 0.4 between our box and between our moving surface and this is dragging the box forwards using friction and then our box is going to begin accelerating with the conveyor until it leaves the conveyor and impacts the floor which has a different coefficient of friction like so and if we were to attach another conveyor perhaps one that wasn't running then our load would begin to decelerate with the same principle until it slows down on this surface just here as the loads impact with each other they're transferring a force between them causing the loads to gently shuffle forward due to the back pressure just here now sometimes it's unnecessary or even inconvenient to run our model using this full physics simulation so instead at any time we can change our run mode to use one of the discrete event simulation engines instead so rather than our loads moving along due to forces applied to them instead what we'll do is we'll use this discrete event simulator to look at where the load is and what it's touching if it's on a conveyor surface or a vehicle or a robot and just move it according to that behavior rather than the forces so we know our loads on a moving conveyor surface so it moves at that conveyor speed you can see that it produces the same behavior as we were seeing on volumetric physics but it much simplifies the calculations so our simulation can run much faster our loads are not going to tumble and overend and whilst they'll accumulate up against each other if we stop this conveyor they're not going to push up against each other providing back pressure as such so we're producing an approximation to the right behavior that's often enough for our simulation needs we can take this to the next step by running our linear physics engine which is only available for some license types not only is this going to be even faster to run but it even takes out the complications of things like mergers so rather than having our loads anywhere on the conveyor they're going to be put straight in the middle of the conveyor each time but our linear engine is going to manage all of this merge behavior for us full information on all of the physics modes can be found on the manual just here now the physics mode that you'll want to use depends upon your application sometimes this level of detail is important you want to see if your say merge behavior will work correctly or if loads will become snagged and we want to have all of this physics information in our system other times it's unimportant and we can simplify our simulation by running in a discrete event engine like linear physics and this example just here shows that linear physics even manages merges for you customizable of course