Circular Motion

Circular Motion

Circular motion is commonly seen in both microscopic and large systems. Motion of the electron, planetary motion and rotation of tyres are common examples of circular motion. What is circular motion? It is a type of motion exhibited by a particle or set of particles moving around a fixed point at a constant distance from that point.

A body that travels an equal distances in equal amounts of time along a circular path has a constant speed but not constant velocity. This is because velocity is a vector and thus it has magnitude as well as direction

The velocity of P is directed along the tangent at P. The speed remains constant but the velocity has changed. We know that if the velocity changes with time then the ball on the string is also accelerating.

The Radian

angles can be measured in radians as well as degrees. The angle in radians is defined by. If s = r then θ=1 rad. Therefore, 1 rad is the angle subtend at the center of a circle by an arc equal in length to the radius. When s =2π r then θ=2 π radians=360°. Therefore, 1 rad = 360°/2 π=57.3°
θ = s/r 

Since we are often dealing with angles and trigonometric functions, a useful approximation that is often used is that for small angles of &theta, sin θ and tan θ = θ where θ is measured in radians.