## 9. Motion and Types of Motion

In our day-to-day life, we see many moving objects. Moving objects are said to be objects in motion. Discuss which objects in the above pictures are in motion. What differences are seen in their motion?

Motion

While waiting for a bus at a bus-stop, other vehicles appear to be in a state of motion. On the other hand, when you are in motion yourself, a still object appears to be moving. For example, the trees are seen to run backward while you are travelling in a train. If an object is seen by an observer to change its place continuously, the object is said to be in motion. Change of place of an object is called displacement. An object in motion continuously undergoes displacement.

Types of motion

1. Linear motion A train or a moving vehicle on a road may travel in a straight line or in the same direction. This motion of an object is called linear motion. An object in linear motion shows displacement along a straight line. If you stand on a chair and release a ball from your hand, it falls to the floor. What do you conclude from this ?

The motion of soldiers in a parade is the same. During that period, not even a slight difference is seen. However, the motion of the girl coming down the slide does not appear to be uniform. The girl comes down faster and faster. The speed of her motion goes on increasing continuously.

The motion of the marching soldiers is ‘uniform linear motion’, because in this motion no change is seen. On the other hand, the motion of the girl coming down the slide is ‘non-uniform linear motion’. These are the two main types of linear motion.

1. Non-linear motion : The motion of an object that does not move in a straight line is called ‘non-linear motion’. Non-linear motion may be of the following types.

What kind of movement does a swing in a park show? The swing always comes back from one end to the other end. It takes about the same time for each swing or oscillation. This movement of a swing is called oscillatory motion. Similarly, the movement of the pendulum of a clock, the wings of a bird, the needle of a sewing machine, the vibrating diaphragm of a tabla or drum are also examples of oscillatory motion.

The hands of a clock move in a circular manner. Similarly, a fan, a giant wheel, and a merry-go-round complete each round along a circular route. In our day-to-day life we come across many examples of objects that trace a circular path.

Which other examples of circular motion can you give ? We see from these examples of oscillatory motion and circular motion that some objects complete one round or one oscillation in a fixed period of time. For example, the minute hand of a clock completes one round in exactly 60 minutes every time, while a merry[1]go-round also completes every round in the same period of time. Such motion is called periodic motion.

While chasing a butterfly in a garden,do you run along a definite path or in the same direction all the time ? Not really. A butterfly constantly flits from one flower to another. There is no definite direction to its motion. Such motion is called random motion

The motion of the players in a game of football is also of this type. The motion of a crawling baby or a wandering animal is also random motion.

Speed

A bus covers the distance of about two hundred kilometres from Solapur to Pune in five hours. How much distance does the bus cover in one hour ? While solving this example, we take the ratio of the distance traversed and the time required to traverse that distance. From this ratio, we come to know the distance traversed by the bus in one unit of time