Is it normal to hurt while urinating after an appendectomy?

No. It is common practice to place a foley catheter during laparoscopic appendectomy procedures to deflate the bladder at many institutions. A known risk of foley catheter placement is a uti. Sounds like you may have one. Speak with your doc for treatment.
No. A catheter may have been placed during the appendectomy and subsequently removed. There may be some burning related to this or there could be a urinary tract infection. You should describe these symptoms to your physician so that a urine culture may be obtained. He/she may also precribe medication to help ease the burining sensation.