An object with a mass of # 12 kg# is lying on a surface and is compressing a horizontal spring by #50 cm#. If the spring's constant is # 6 (kg)/s^2#, what is the minimum value of the surface's coefficient of static friction?
The situation here is that the spring is already compressed by
That means force of friction and spring force are balancing each other out.
Spring forces is
Now, frictional force depends on the normal force of the body. Since the surface is horizontal, the entire weight of the body is the normal force. So,
Equating the two,
So, that's how the minimum static constant is so small.