Momentum is not conserved if there is friction, gravity, or net force (net force just means the total amount of force). What it means is that if you act on an object, its momentum will change. This should be obvious, since you are adding to or taking away from the object's velocity and therefore changing its momentum.
Somerville, Massachusetts. Somerville (/ËsÊmÉrvÉªl/ SUM-Ér-vil) is a city located directly to the northwest of Boston, in Middlesex County, Massachusetts, United States. As of 2010, the United States Census has the city with a total population of 75,754 people, and is the most densely populated municipality in New England.
Over 80% of Massachusetts' population lives in the Greater Boston metropolitan region. Greater Boston is ranked tenth in population among U.S. metropolitan statistical areas, home to 4,732,161 people as of the 2014 U.S. Census estimate, and sixth among combined statistical areas, with a population of 8,099,575.