Maharashtra Board Class 6 Science Chapter 9 Motion and Types of Motion PDF Download

Motion And Types Of Motion

Observe And Discuss

Objects In 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.

The continuous displacement of an object is called motion.

Teacher's Note

When you sit in a train and see trees moving backward, it looks like trees are moving. But really, you are moving. Things appear to move because you change your place.

Exam Trick

Remember: Motion = Change of place. When your position changes, you are in motion.

Points To Remember

Motion means an object changes its place continuously.
Displacement means the change in position of an object.
Motion and displacement are connected to each other.

Types Of Motion

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?

Teacher's Note

When you drop a ball from a height, it falls straight down. This is linear motion because the ball moves in one straight line direction.

Exam Trick

Remember: Linear = Line. Linear motion is always in a straight line.

Points To Remember

Linear motion is motion in a straight line.
The object moves in only one direction.
A falling ball shows linear motion.

Comparing Linear Motion

Compare the motion of soldiers on parade and a girl coming down a slide.

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.

Uniform linear motion
When the distance traversed by an object along a straight line in unit time is continuously the same, the motion is called uniform linear motion.

Non-uniform linear motion
When the distance traversed by an object along a straight line in unit time keeps on changing, the motion is called non-uniform linear motion.

Teacher's Note

When soldiers march, they all walk at the same speed. This is uniform motion. But when a girl slides down, she goes faster and faster. This is non-uniform motion.

Exam Trick

Remember: Uniform = Same. In uniform motion, speed does not change. In non-uniform motion, speed keeps changing.

Points To Remember

Uniform linear motion has the same speed always.
Non-uniform linear motion has changing speed.
A car on a highway at constant speed shows uniform motion.

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.

Oscillatory Motion

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 motion of a body that is oscillating, i.e., swinging back and forth, is called oscillatory motion.

Teacher's Note

A swing moves back and forth. A pendulum swings left and right. Both movements are oscillatory motion. We see this in many things around us.

Exam Trick

Remember: Oscillatory = Back and forth. Think of a swing in a park moving side to side.

Points To Remember

Oscillatory motion is swinging back and forth.
The object moves in both directions.
A clock pendulum shows oscillatory motion.

Circular Motion And Periodic 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-go-round also completes every round in the same period of time. Such motion is called periodic motion.

The motion of an object along a circular path is called circular motion.

The motion of an object which passes through a certain point again and again after a fixed period is called periodic motion.

Teacher's Note

A fan blade goes round and round in a circle. The hour hand of a clock also moves in a circle. Both show circular motion. The clock hand comes back to the same place every 12 hours, so it is also periodic motion.

Exam Trick

Remember: Circular = Round path. Periodic = Repeats at fixed time. A merry-go-round shows both.

Points To Remember

Circular motion is motion along a round path.
Periodic motion repeats after a fixed time.
The hands of a clock show both circular and periodic motion.

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