Exam (elaborations) object is said to have non-uniform motion if it tr

 Speed of a body is defined as the distance travelled by the body in unit time. The SI unit of speed is metre/second (m/s). Distance travelled Speed Time taken  If ‘s’ is the distance travelled by a body in time ‘t’, then its speed ‘v’ is given as s v t  Speed of a body is a scalar quantity. It can be zero or positive but can never be negative.  If a body covers equal distances in equal time intervals, howsoever small the intervals may be, then it is said to have uniform speed (or constant speed).  If a body covers unequal distances in equal time intervals, however small the intervals may be, then it is said to have non-uniform speed (or variable speed).  For bodies moving with non-uniform speed, we describe the rate of motion in terms of their average speed. Total distance travelled Average speed= Total time taken Motion Uniform motion Non-uniform motion PHYSICS MOTION 4 Velocity  Velocity of a body is defined as the distance travelled by the body in unit time in a given direction.  The SI unit of velocity is the same as that of speed, i.e. metre/second (m/s). Distance travelled in a given direction Velocity Time taken Displacement or, Velocity Time taken s i.e. v t where v is velocity and s is displacement of the body in time t.  Velocity of a body is a vector quantity. It can be positive, negative or zero.  A body is said to be moving with uniform velocity (or constant velocity) if it travels along a straight line, covering equal distances in equal intervals of time, howsoever small these intervals may be.  A body is said to be moving with non-uniform velocity (or variable velocity) if it covers unequal distances in a particular direction in equal intervals of time or if the direction of motion of the body changes.  When the velocity of a body is changing at a uniform rate over a period of time, the average velocity for that time period is given by the arithmetic mean of the initial and final velocity of the body. av Initial velocity + Final velocity Average velocity 2 u v or v 2 where ‘u’ is initial velocity, ‘v’ is final velocity and vav is average velocity. PHYSICS MOTION 5 Acceleration  Acceleration of a body is defined as the rate of change of its velocity with time. Change in velocity Acceleration Time taken Final velocity - Initial velocity Time taken v - u or, a t where ‘u’ is initial velocity, ‘v’ is final velocity, ‘a’ is acceleration of the body and ‘t’ is time taken for change in velocity.  Acceleration is a vector quantity. It can be positive, negative or zero. The SI unit of acceleration is metre per second square (m/s2 ).  If the velocity of a body increases, then the acceleration is positive. If the velocity of a body decreases, then the acceleration is negative. Negative acceleration is called retardation.  If acceleration occurs in the direction of velocity, then it is taken as positive and negative when it is opposite to the direction of velocity.  A body is said to possess uniform acceleration if it travels in a straight line and its velocity increases or decreases by equal amounts in equal intervals of time.  A body is said to possess non-uniform acceleration if its velocity changes by unequal amounts in equal intervals of time