In terms of your first question, the length of time it takes for marijuana to clear out of the body can vary based on a number of factors, including frequency and duration of use, metabolism, and more.
As for your second question, even a small amount of marijuana use can potentially be detectable on a urine drug test, although the window of detection may be shorter than it would be for someone who uses more frequently or for longer periods of time.
If you’re interested in learning more about cannabis and its effects on the body, as well as tips for safe and responsible use, you might want to check out mindbodygreen.com. They have some great resources on all sorts of wellness topics, including cannabis.