In the 3D Mechanics Editor you can enter the mass, inertia and geometry using hard coded numbers. E.g:
Mass: 8 kg
Now you can run a simulation and see the result. But suppose you are not happy with the results and want to see the effect of a 6 kg mass? Then you have to return to the 3D Mechanics Editor, enter the number 6, process the model and run a simulation. This takes a lot of time. It would be nice if the mass was just a parameter that you change during simulation. This is called parametric modeling.
In the 3D Mechanics Editor can enter the mass as an Expression. E.g:
Mass = Car_weight
where Car_weight is a parameter which you can give a certain value. Now before the simulation, you can simply change the the value of the parameter Car_weight and inpsect the results. With expressions, you can do more. E.g.:
Mass = Car_length * Car_length * Car_width * rho_steel / 100
Now we have coupled the mass to a expression which contains other parameters. Now we can run a simulation and simply change the dimensions of the car and see the results.
Everwhere in the 3D Mechanics Editor, where you have to enter numbers, there is an option to enter an expression. For example if you want to enter the mass of a body, you have to open the Inertia Properties. You can enter the mass as a value directly but also choose to use an Expression to define its value.
If you click the Expression button, the Expression Editor opens, allowing you to enter the expression.