The magnitude and direction of the force of a spring that restores its shape can be predicted by what is called Hooke’s Law.
The direction of the force is always towards the relaxed position of the spring i.e against the motion of spring (hence the minus sign). is the spring constant. is the extension of the spring.
The centripetal force on an object in circular motion is always towards the center of the circle and can be calculated by
Where is the centripetal acceleration which I discussed in Chapter 4.
Note: I am not sure whether the force due to air resistance should be included at this point. I might append it to this chapter later.