Types of motion

Distance
Distance is the actual path travelled by a body in a given time. Consider a body travelling from A to B along any path between A and B. The actual length of the path that a body travels between A and B is known as the distance. Here if the body goes from A to B via C, the distance travel will be ACB. The distance travelled will be different for different paths between A and B.

Speed 
The distance travelled by a body in unit time is called its speed. 
Therefore, speed = Distance/Time

(a)    Uniform Motion : A body has a uniform motion if it travels equal distances in equal intervals of time, no matter how small these time intervals may be. For example, a truck running at a constant speed of say, 20 m/s, will cover equal distances of 20 metre, in every second, so its motion will be uniform.
                                        Or
If it moves along a straigth line with a constant speed it is said to be in uniform motion.

(b)     Non-Uniform Motion : A body has a non-uniform motion if it travels unequal distances in equal intervals of time. For example, If a car moving on a highway , we will find that it covers unequal distances in equal intervals of time. It covers :
5.9 metre in the 1st second,
15.7 metre in the 2nd second,
30 metre in the 3rd second, and so on.
                                 Or
If the speed of an object is not moving along a straigth line  keeps changing, its motion is said to be non-uniform.

Uniform and Non-uniform motion can be shown graphically also

 Ex. 3 A body satrts from A and moves according to given figure. Time for each interval is : 

t_AB = 2s, t_BC= 3s, t_CB=2s, t_BA = 3s, t_AD= 4s

The distance, speed are as follows for different path.

Ex.4    A car travels a distance of 100 Km in 25 minutes to reach a place then calculate the speed of the car : 
(A) 4 km/min         (B) 4 m/min          (C) 400 m/min         (D) None of these

Ex.5     If an object  travels with the speed 18 km/hr for 20 minute find the distance covered by the object.
Sol.    Speed = 18 km/hr, time = 20 min
    Distance = speed × time