Motion and Its Types Class 7

Motion

a) Motion is the way objects or things move from one place to another. It's all about how things change their position or location over time.
b) For example, when you walk, run, or ride a bike, you are experiencing motion.
c) There are different types of motion. Some objects move in a straight line, like a car driving on a road. Some objects move in a circular path, like a spinning top. Others move back and forth, like a swing. These different ways objects move are called different types of motion.
d) Motion can also be uniform or non-uniform.

Uniform and Non-Uniform Motion

Types of Motion with Examples

1. Translatory Motion

a) Translatory motion refers to the movement of an object in a straight line. It involves the displacement of an object from one position to another without any rotation.
b) For example, a car moving along a straight road or a ball rolling on a flat surface.

Translatory motion can be further classified into different types based on the nature of the path followed by the object:

1. Linear Motion: Linear motion refers to the movement of an object along a straight line. Examples include a car moving along a straight road or a person walking in a straight line.



2. Curvilinear Motion: Curvilinear motion refers to the movement of an object along a curved path. The path can be a circle, an ellipse, or any other curved trajectory. Examples include a car moving along a curved road or a satellite orbiting around a planet.

2. Circulatory Motion

a) Circulatory motion involves the movement of an object in a circular path around a fixed point or axis.
b) Examples of circulatory motion include the spinning of a top, the rotation of the Earth around its axis, or the movement of a Ferris wheel.

Circulatory motion can also be classified into different types based on the axis of rotation and the nature of the circular path:

1. Rotational Motion: Rotational motion involves the spinning or rotation of an object around its own axis. Examples include the spinning of a top, the rotation of a ceiling fan, or the turning of a steering wheel.



2. Orbital or Revolutionary Motion: Orbital motion refers to the movement of an object in a circular or elliptical path around another object. Examples include the moon orbiting around the Earth or planets revolving around the Sun.

3. Oscillatory Motion

a) Oscillatory motion is when an object moves back and forth repeatedly around a central position. It's like a swinging motion or vibrations that go back and forth.
b) You can think of it as something that moves between two extreme points. For example, when you swing on a swing set, it moves back and forth, and that's an example of oscillatory motion.
c) Oscillatory motion can be categorised into two types:

i) Simple Harmonic Motion (SHM)

a) In SHM, the object moves back and forth in a way that the force pulling it back to the centre is directly proportional to how far it is from the centre.
b) It's like a rubber band pulling something back towards the middle.
c) Examples of SHM include the swinging of a pendulum (like a grandfather clock).

ii) Damped Oscillation

a) Damped oscillation is a type of oscillatory motion where the back-and-forth motion gradually becomes smaller and eventually stops due to the presence of forces like friction or air resistance.
b) It's like when you swing on a swing, but someone applies a brake or holds onto the swing, causing it to slow down and eventually stop.
c) This is seen in situations where there is resistance or something slowing down the motion. An example of damped oscillation is the motion of a guitar string that gradually fades away.

4. Repetitive Motion

The repetitive motion refers to any motion that is repeated over time. It can be further divided based on the nature of the repetition:

i) Periodic Motion

a) Periodic motion is a type of repetitive motion in which the motion is repeated at regular intervals of time.
b) It follows a specific pattern.
c) Examples include the oscillation of a pendulum, the rotation of the Earth around its axis, or the heartbeats.

ii) Non-Periodic Motion

a) Non-periodic motion is a type of repetitive motion in which the motion is not repeated at regular intervals.
b) The pattern may be irregular or unpredictable.
c) Examples include the motion of ocean waves, the movement of a car in city traffic, or the flickering of a candle flame.

5. Random Motion

a) Random motion, also known as chaotic motion, refers to the unpredictable and irregular motion of an object.
b) It lacks any specific pattern or order.
c) Examples of random motion include the movement of gas molecules or the flight pattern of a butterfly.

Distance and Displacement

Distance

a) Distance refers to the total length covered by an object during its motion. It's like measuring how much ground an object has covered from start to finish, regardless of the direction.
b) For example, if you walk around a park in a circle, the distance you covered would be the entire length of the circle you walked.
c) Distance can be measured using various units, such as metres (m), kilometres (km), centimetres (cm), or even miles. The most common unit for measuring distance is metres. In our daily lives, we often use metres to talk about distances.

Displacement

a) Displacement, on the other hand, is a measure of the change in position of an object. It takes into account both the distance and the direction of the movement from the starting point to the ending point.
b) Displacement is like drawing a straight line from the starting point to the ending point, regardless of the actual path taken.
c) For example, if you walk from your house to the park and then return back to your house, your displacement would be zero because you ended up in the same position where you started.

Differences between Distance and Displacement

Frequently Asked Questions

1. Can an object have non-uniform motion even if it travels along a straight path?

Yes, an object can have non-uniform motion on a straight path if its speed changes along the way. For instance, a cyclist moving on a straight road but accelerating and decelerating experiences non-uniform motion.

2. How can two objects cover the same distance but have different displacements?

Two objects can cover the same distance but have different displacements if they move in different directions. For example, if one object travels 10 metres in a straight line and another object travels 10 metres in a curved path, their displacements may be different.

3. What are the differences between oscillatory and periodic motion?

Oscillatory Motion:

1. Oscillatory motion refers to the back-and-forth movement of an object around a central point or equilibrium position.
2. The motion alternates between two extreme points, crossing the equilibrium position multiple times.
3. Examples include the swinging of a pendulum, the vibration of a guitar string, or the bobbing of a buoy in the ocean waves.

Periodic Motion:

1. Periodic motion refers to any motion that repeats itself at regular intervals of time.
2. It may or may not involve oscillation around a central point.
3. Periodic motion can be oscillatory, but it can also include other repetitive motions such as circular motion or rotational motion.
4. Examples of periodic motion include the Earth's rotation on its axis, the orbit of planets around the Sun, or the spinning of a wheel.

4. What is Inertia?

Inertia refers to an object's tendency to resist changes in motion. It is the reason that objects remain at rest or move at a steady speed unless moved upon by an external force.

5. What is the significance of direction in displacement, and why is it considered a vector quantity?

Displacement is considered a vector quantity because it has both magnitude (distance) and direction. The direction is important because it tells us the shortest path between the starting and ending points, not just how far the object has travelled.