Building LEGO Rollercoasters and Programming

We had a super Science and Technology day using LEGO to build our rollercoasters.  First of all, we used the LEGO to build our track and then we tested our rollercoaster from the launcher to see if it would stay on the track. 

We then used LEGO We do to program a sensor which had a windmill attached to it.  We put our sensor next to the track and every time the rollercoaster went past the sensor, the windmill would spin.