Torque and angular momentum with a central force

[fer Mnaj]

Homework Statement

Consider the central force $F (r) = - k / r^2 ˆr$ to which a particle of mass m is subject; where ˆr is the unit vector along the line connecting the center of forces with the position of the particle. Calculate the torque that F exerts on m and the angular momentum of the particle;
Calculate the torque that F exerts on m and the angular momentum of the particle;
both quantities with respect to O

Relevant Equations

τ= r x F L=rxp

HI

τ= r ˆr x - $k / r ^ 2$ ˆr= 0 right? since ˆr x ˆr is zero

What about L?

 

[BvU]

As you say, $\vec L = \vec r \times \vec p$ . If you have no further information, that's it.