Homework-pan with moving object, blur background

Photography homework- set camera to S for shutter priority, set the speed to slow, about a fortieth. Pan with a moving object, get the background to blur. Sounds easy doesn't it.
First of all, I couldnt find a moving object- thought a dog would be nice but I haven't got one- that had a nice clear view in front of it. There were loads of pedestrians. Anyway I will stop moaning, this is my best effort after half and hour of trying.