# NCERT Chapter Summary: Motion in a Plane

Motion in a plane is the motion in two dimensions, for instance, projectile motion, circular motion and so on.

Scalar Quantities: Scalar quantities are those physical qualities that can be specified completely by their magnitude alone. The examples of scalar quantities are mass, density, temperature, length, work, speed.

Vector Quantities: Vector quantities are specified by both magnitude and direction. The examples of vector quantities are displacement, acceleration, momentum, velocity, torque, force. The direction of any vector quantity is specified by a unit vector.

Projectile motion is one of the most common examples of motion in a plane. When an object moves in a circular path at a constant speed, then the object is said to be in a uniform circular motion.

Time Period: The time period of uniform circular motion is the time taken by an object to complete one complete revolution in its circular path. To maintain an object in its uniform circular motion, a radially inward acceleration must be maintained continuously, it is called centripetal acceleration.