Magnetic force obeys an inverse square law with distance. ... If the distance between two magnets is halved the magnetic force between them will increase to four times the initial value.
Answer: 1.76 Nm
Explanation:
If the force pulls horizontally, this means that the force is tangent to the disk at any point of the string unwinding process, so the distance d is irrelevant.
In this case, the torque is directly given by the product of the force times the distance perpendicular to the center of the disk, which is just the radius, as follows:
τ = F * r = 16 N. (0.11) m = 1.76 Nm
It holds the atoms together (aka your last option)