1. FORCE AND MOTION - II
Friction
Until now we ignored friction but it must be taken into account in most situations.

2. If the body is not moving:
If the body is moving:
Fs and Fk are always parallel to the surface and opposed to attempted sliding

8. UNIFORM CIRCULAR MOTION

9. A centripetal force accelerates a body by changing the direction of the body’s velocity without changing the body’s speed.
Centripetal force is not a new kind of force. It indicates the direction of the force. It can be friction force, tension e.t.c.

10. Conical Pendulum

12. The Drag Force and Terminal Speed
When an object moves through a liquid or a gas (such as air), the fluid resists the motion of the object and the resistive force or drag force depends or the velocity of the object.