In the chapter on angular momentum, torque is expressed as: In the previous chapter, it was ττ = Ftr. Please explain what is similar and what is different about these two definitions of the same quantity.

τ = r x F,   τ = dL / dt .  second definition we have the body mass that could change, so it is a more general definition than the first one that only considers a body of constant mass

Explanation:

The moment is defined by

         τ = r x F

Where x represents the vector product, in this case the body is assumed to be rigid, this means that the distance r is constant

Torque can also be defined by

            τ = dL / dt

            L = r x p

            p = m v

           τ = d (r x m v) / dt

           τ = r x d (m v) dt

In this second definition we have the body mass that could change, so it is a more general definition than the first one that only considers a body of constant mass

a lot of it means it can be "burned" for energy and sold at one price. if it is scarce, the price will go up