Simulink Diagram for Solving a Nonlinear Second-Order Differential Equation

[theone]

< Mentor Note -- thread moved to HH from the technical engineering forums, so no HH Template is shown >

[itex]\frac{d^2 \theta}{dx^2}=-\frac{x}{10}\cos \theta - \frac{9.8}{10}\sin \theta[/itex]

I'm supposed to draw a simulink diagram for this equation and find the response to a unit step function

This is what I did so far but I don't know if its right
http://postimg.org/image/64mm8rjhv/

 

[donpacino]

looks good. typically i like to arrange the block diagram so the input is on the left, but that is just a matter of preference.

 

[theone]

looks good. typically i like to arrange the block diagram so the input is on the left, but that is just a matter of preference.

thanks Also, I'm supposed to find the response to a unit pulse function.
But when I replace the step function with a pulse generator and try running, I get this:
"Using a default value of 0.2 for maximum step size. The simulation step size will be equal to or less than this value. You can disable this diagnostic by setting 'Automatic solver parameter selection' diagnostic to 'none' in the Diagnostics page of the configuration parameters dialog"

 

[donpacino]

is that a warning or an error.
typically that step size refers to the simulation step size in the solver. Go to simulation;model config parameters and you can change the step sizes. You can also change it from variable to set step sizes, which i typically recommend.