This technique is called "zoom burst." You take a long exposure and zoom in or out while the shutter is still open. With just a little practice and experimentation, it's a really easy effect to achieve.
*college work* By using a slow shutter speed you can capture a zoom burst by pressing the shutter release and then zooming in on the centre of your subject - a shutter speed of about seconds would be enough to capture something like this.
How to Take Photos with the Zoom Blur Effect [Includes Printable Cheat Sheet]