The collision took place on the B2149 Petersfield Road, near the junction with Wakefords Way, sometime between 12.45pm and 1pm on Monday 23 November.
A Peugeot moped and a dark Vauxhall saloon car were in collision. The driver of the car then exited his vehicle and shouted at the rider before driving in the direction of Rowlands Castle.
The rider, a 20-year-old man, sustained a fractured ankle in the collision and received treatment at the hospital.
The car driver is described as white, around 40 to 45 years of age, of skinny build, around 5ft 7ins tall, with dark, greying short hair and tattoos on his arms and chest.
A second man also exited the car briefly during this incident. He is described as white, aged in his mid 20s, of skinny build, dirty blond long hair, and was wearing glasses.
We are keen to hear from anyone who saw what happened or has any further information.
Were you driving along this road? Did you see the collision, or did you see the vehicles before or after the collision took place?
Perhaps you have dashcam footage that may help our enquiries?
Anyone with information should call us on 101, quoting the reference number 44200453697.