What is a likely cause of a 2 week old with projectile vomiting and no fever?

See your MD. It could be a couple things, but the one the pediatrician needs to r/o is pyloric stenosis or non accidental trauma. Reflux is also a possibility.
Pyloric stenosis. Anytime a parent describes projectile vomiting, that child needs to be seen. Pyloric stenosis is a congenital problem where the outlet of the stomach thickens over the first months or so of life and creates an "outlet obstruction" leading to projectile vomiting. It is easily diagnosed with an ultrasound and is easily repaired surgically. This child needs to be seen.
Pyloric Stenosis. A full term child who is vomiting forcefully and not able to keep feeds down should be evaluated immediately. They may have an obstruction of the stomach which prevents the food from leaving the stomach. Please consult your physician immediately.

Related Questions

3wk old projectile vomiting no fever but not keeping anything down, ultrasound was good. What else should drs be looking for?

Watch closely. Breastfeed or not? The chief concern is a newborn condition called pyloric stenosis. A normal ultrasound is reassuring, but does not completely rule it out. The baby needs to be watched closely to see what happens to the weight. Also make sure burping the infant frequently is done.