Pressure and Motion

This concept mainly deals with pressure and types of motion. After reading the concept, students will be able to:

Explain different types of motion and understand what is periodic motion and state periodic motion examples.
Answer what is rectilinear motion and give rectilinear motion examples,
State what is rotational motion with rotational motion examples
Define oscillatory motion with examples.
Know about what is uniform motion, example of uniform motion.
Mention what is non uniform motion and examples of non uniform motion.
Analyse the difference between uniform and non uniform motion.
Explain why do gas exert pressure?

Each concept is explained to class 4 students using descriptions, illustrations, and concept maps. After you go through a concept, assess your learning by solving the two printable worksheets given at the end of the page.

Download the worksheets and check your answers with the worksheet solutions for the concept of the Pressure and Types of Motion provided in PDF format.

What is Pressure?

Pressure is defined as the force exerted per unit area.
It depends on two factors—force and area.
If the exerted force is high, the pressure will also be increased.
When a force acts over a large area, pressure will be less, whereas pressure will be high if a force acts over a small area.
Pressure is directly proportional to force and inversely proportional to area.

Examples:

Why do trucks and tractors have wide tyres?

Trucks and tractors have wide tyres because they have a large area, for which less pressure is exerted on the ground.

Tractors are used in agricultural fields because, due to the reason mentioned above, the tyres do not sink into the soil.
Similarly, hammering a sharp nail is easier; school bags with wide straps create less pressure on our shoulders, and a sharp knife can cut better than a dull knife.

Pressure exerted by liquids:

The molecules of a liquid exert pressure in all directions.
The liquid molecules exert pressure on the walls of the container in which they are poured.
The intensity of sideways pressure increases along with the depth of the container.
The liquid molecules also exert pressure at the bottom of the container.
The pressure on the bottom of the container increases as the height of the liquid increases in the container.

Pressure exerted by gases:

Gas molecules also exert pressure in all directions like liquids.
Gas can be compressed in a container.
When a balloon is inflated, it becomes bigger due to the pressure of the gas molecules, whereas a deflated balloon shrinks and has little or no gas inside it to put pressure on its walls.
The pressure exerted by gas molecules increases when the temperature increases and decreases when the temperature decreases.
The volume of the gas increases when pressure is low and decreases when pressure is high.
We can say that pressure exerted by a gas is directly proportional to temperature but inversely proportional to volume.

Atmospheric pressure:

We all know that gravity pulls air towards the earth.
So, we can say that atmospheric pressure or air pressure is the force exerted by the air around us.
Air pressure also acts in all directions.

What is Motion?

The phenomenon of an object moving or being moved is called motion.
Force can initiate the movement of an object as well as it can stop a moving object.

Types of motion:

Types of motion	Explanation
1. Rectilinear motion	When motion occurs in a straight line, it is called linear motion. Example: Motion of a man running.
2. Circulatory motion	When motion occurs in a circular path, it is called circulatory motion. Example: Motion of the minute hand of the clock.
3. Rotational motion	When motion occurs in a rotational path, it is called rotational motion. Example: Motion of a soccer ball in a soccer match.
4. Periodic motion	When motion occurs in a periodic path, it is called periodic motion. Example: Motion of a simple pendulum.

New Words:

Directly proportional: When one quantity becomes larger or smaller, the other quantity becomes larger or smaller.

Inversely proportional: When one quantity becomes larger, the other becomes smaller and vice versa.

Did You Know?

When a body travels equal distances in equal intervals of time, it is called uniform motion. When a body travels unequal distances in equal intervals of time, it is called non-uniform motion.