You need to make a spring scale to measure the mass of objects hung from it. You want each 1.0 cm length along the scale to correspond to a mass difference of 0.10 kg. What should be the value of the spring constant?

The spring constant should be:

Explanation:

Use Hooke's law for this problem, knowing that the magnitude of the force (F) on the spring equals the stretching it experiences times the spring constant "k":

in our case, since the mass hanging is given in kg, we need to multiply it by "g" to get the force exerted:

Then if we add to the spring in its relaxed state, a mass of 0.10 kg, and we want for that a displacement of 1 cm (0.01 m), then the value of the spring constant should be:

There is no field linked with the contact force. There is always a field linked with non-contact force. The frictional force is an example of a contact force. Gravitational force is an example of a non-contact force.