If a skater is a rigid body, how can we apply Newton's second law? I understand how it works if the skater was a pontual body, but i'm not sure how it's going to work if we consider her as an exetended body.
How come the torque of the net force be zero? In Why does a ballerina speed up when she pulls in her arms? it's mention that:
Fr is the centripetal force towards the center of the osculating circle that curves the arm's path, and Ft is a (small) tangential force in the direction of motion that speeds the arm up.
but I still remain clueless about what does that imply because acting on the skater. So what forces are acting on the skater?
- If she is actually a rigid body she while be a particle aggregate, which makes sense beacuse we are considering the distribution of her mass. So we know that her global mass will be the Summation of the masses of her particules, but this particules have different radius to the center of mass. So when we are looking at the spin of the skater how do we take in consideration the r? Do we just considere it zero? That would make the torque zero... I really don't know
edit: please don't use polar coordinates, i don't really know how they work