Motion:-The change of position of an object with respect to time. Change in motion is the result of an applied force.
In physics, change in motion is the result of an applied force. An object of the velocity cannot change unless it is acted upon by a force. The momentum of an object is directly related to the mass, velocity and the total momentum of all objects in a closed system.
Types of Motions
1. Rotation Motion
2. Circular motionrotational motion
Rotation motion:- Irrespective of path, if a particle moves around a fixed point then that motion is called rotati onal motion.
Ex: Motion of earth around the sun in elliptical orbit is rotational.
Circular motion:- If the path of rotating particle around a fixed point is a circle then it can be called as circular motion.
circular motion
Ex: 1)If a small body is tied to a string and whirled round a fixed point. Then it is purely a circular motion.
2)Motion of moon around the earth.
Types of Rotations:
Center of Rotation
Axis of Rotation
Centre of rotation:- The fixed point around which the particle is making rotational motion is called centre of rotation.
Axis of rotation:- A line passing through the centre of rotation and perpendicular to the plane of rotation is called axis of rotation.
Types of Forces
Centripetal force: Centripetal force is unbalanced force required by a body to perform uniform circular motion. Centripetal force is always directed towards the centre.
A body moves with the centripetal force and moves a curved path. It is always directed orthogonal to the velocity of the body, toward the instanaeous center of curvature of the path.
Formula:-
F= ma_c = mv^2/r
Formula for force
Where m is mass of the object
v is the velocity
r is the radius of curvature
Centrifugal force: A particle is moving along a circle, the pseudo force which acts radially away from the centre and equal in magnitude to the centripetal force is called centrifugal force.
It is a pseudo force (or ) fictitious force when we are in a non inertial frame of reference.
Definition of Couple, Centripetal Acceleration
Couple: Two equal unlike and non collinear forces acting on a body constitute a couple and produce rotation.
Moment of couple is defined as a product of either of the forces and perpendicular distance between their lines of action.
Units: Nm(in SI System)
Centripetal acceleration: When a particle is moving along a circle of radius r with a uniform speed v then due to change in direction of velocity, the particle possesses an acceleration directed towards the centre called centripetal acceleration.