REVIEW AND SUMMARY FORCE AND MOTION 11

REVIEW AND SUMMARY FORCE AND MOTION 11

Friction When a force F tends to slide a body along a surface, a frictional force from the surface acts on the body. The frictional force is parallel to the surface and directed so as to oppose the sliding. It is due to bonding between the body and the surface.

Three Properties of Friction

1. If the body does not move; then the static frictional force?, and the component of F that is parallel to the  surface are equal in magnitude.

2. If the body begins to slide on the surface, the magnitude of the frictional force rapidly decreases to a constant.

Drag Force When there is a relative motion between air (or some other fluid) and a body, the body experiences a drag force that opposes the relative motion and points in the direction.

Terminal Speed When a blunt object has fallen far enough through air, the magnitudes of the drag force and the gravitational force  on the body become equal.

Uniform Circular Motion If a particle moves in a circle or a .circular arc with radius R at constant speed v, it is said to be in uniform circular motion. It then has a centripetal acceleration a with magnitude.

where m is the particle’s mass. The vector quantities a and Fare directed toward the center of curvature of the particle’s path.