# Physics

Topics: Classical mechanics, Force, Mass Pages: 2 (624 words) Published: January 29, 2013
In physics, motion is a change in position of an object with respect to time and its reference point. Motion is typically described in terms of velocity, acceleration, displacement, and time.[1] Motion is observed by attaching a frame of reference to a body and measuring its change in position relative to another reference frame. A body which does not move is said to be at rest, motionless, immobile, stationary, or to have constant (time-invariant) position. An object's motion cannot change unless it is acted upon by a force, as described by Newton's first law. An object's momentum is directly related to the object's mass and velocity, and the total momentum of all objects in a closed system (one not affected by external forces) does not change with time, as described by the law of conservation of momentum. As there is no absolute frame of reference, absolute motion cannot be determined.[2] Thus, everything in the universe can be considered to be moving.[3] Main types of simple motion

There are two types of basic motion: translation and rotation. Translation means motion along a path. Rotation means motion around a fixed axis. An axis is the centre around which something rotates. As we have mentioned before, each type of motion is controlled by a different type of force. Translation is defined by the net force (sum of different forces) acting on an object. Rotation is defined by torque. Torque is a force which causes the rotation of an object. Linear motion is the most basic of all motions. Linear motion is the type of motion in which all parts of an object move in the same direction and each part moves an equal distance. Linear motion is measured by speed and direction. Distance travelled by an object per unit of time is called velocity. Example: a moving car. Rotary motion is motion in a circle. This type of motion is the starting point of many mechanisms. Example: a spinning wheel. Reciprocating motion is back and forth motion. Example: the up and down motion...