Chapter 3: Q45P (page 126)
Two rocks are tied together with a string of negligible mass and thrown into the air. At a particular instant, rock 1, which has a mass of
, is headed straight up with a speed of
, and rock 2, which has a mass of
, is moving parallel to the ground, in the +x direction, with a speed of
. a) What is the total momentum of the system consisting of both rocks and the string? b) What is the velocity of the center of mass of the system?
Short Answer
a) the total momentum of the system consisting of both rocks and the string is
and b) the velocity of the center of mass of the system is

are the mass of the rock 1 and rock 2 respectively and
are the velocity of the rock 1 and rock 2 respectively.




moving with velocity
. At the same instant object 2 is at location
, moving with velocity
. a) what is the location of the center of mass of the two equal mass objects? b) What is the velocity of the center of mass?