Take the spring bumper out of the end of the air track and attach the force sensor to the end with some rubber bands.  Start with the hoop spring on the end of the force sensor.  Place the launcher on the track about 50 to 75 cm away from the force sensor and set it to the desired spring tension.  Place a 1 M, 2 M, or 3 M car against the magnet of the launcher, hit the "collect" button on the interface software, and look at the data when the car hits the sensor.  Specifically, you are looking for the "time of contact" for the collision of the car and force sensor spring as can be seen in picture 3 above.  

There is also an attachment for the force sensor that allows you to look at "time of contact" for an inelastic collision.  When using the same car and spring tension on the car launcher as in the above experiment, you will see that the time of contact is much shorter, but that the force is much larger.