Write down the total momentum for two marbles of mass, m, both moving at velocity, v. what is the kinetic energy of the system.

Mv + mv = 2mv providing each momentum is in the same direction.
1/2 mv^2 + 1/2 mv^2  = mv^2

The momentum of marble-A is (m v).
The momentum of marble-B is (m v)
Momentum is a vector quantity, and we don't know the direction
either marble is moving.  So we don't know how their momenta 
will combine.  The sum of their momenta is something between
zero and (2mv).

The kinetic energy of marble-A is (1/2 m v²).
The kinetic energy of marble-B is (1/2 m v²).
If the marbles are the only matter in the system, then
the total kinetic energy in the system is (m v²). 

answer and explanation;

composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock while texture refers to the size and arrangement of the minerals or grains that make up a rock. both composition and texture can be used to classify rocks, such as igneous rocks. texture describes how the rock became solid or crystallized from liquid, melted rock. composition of a rock describes the minerals that make up a particular rock.