Magnitud del momento de una fuerza respecto a un punto cuando la línea de acción de la fuerza pasa por dicho punto.

  τ = 0

Explanation:

The moment of a force is defined by

          τ = F x r

where bold indicates vectors.

We can write this equation in module form

           τ = F r sin θ

the amount without ea r is called the breaststroke and is the distance perpendicular to the pivot point.

The line of action of the force passes through the turning point whereby

r = 0,

Consequently the moment is also zero

            τ = 0

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.