## Difference Between Thrust and Pressure Class 9

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## Thrust and Pressure

**The difference between Thrust and Pressure** is a common topic in Class 9 Physics. Thrust and pressure are quantities you have studied in earlier classes, but many students find it confusing to define pressure. Is pressure a force per unit area or thrust per unit area? Actually, both definitions can be correct. Thrust and force are similar, but thrust is directed in a particular direction and is a reactive force caused by the surroundings. For example, when you push or pull an object, it’s more accurate to use the term force. Thrust, as defined by Newton’s third law, is essentially the reaction against a force. For instance, a balloon is lifted into the sky due to the thrust created by the pressure difference between the air inside the balloon and the air above it. Understanding **the difference between thrust and pressure** is crucial for grasping various physics concepts.

## What is Thrust?

Thrust is an upward force applied by a surface to a body in contact, which is perpendicular to the surface. At the situation when you stand up, strolling or have various stances what are the forces that keep your balance in these positions while as we probably are aware the gravity acts downwards. When the object is partially or completely submerged into the fluids an upward force is exerted by the fluid on the object which is opposite in direction of the gravitational force, this upward force is known as thrust or buoyant force. This upward thrust generated because of the pressure difference between the upper and lower end of the object as we know the pressure is directly proportional to the depth in a liquid. The case when an object is kept on a surface the gravity acts downwards and as we know that every action has an equal and opposite reaction, this reaction is nothing but an upward force acts on the object by the surface that balances the object in its place.

## What is Pressure?

Thrust or force per unit area is known as pressure.

## Difference Between Thrust and Pressure

Thrust and pressure are related but different concepts.

**Thrust**is the force exerted directly and perpendicularly by a surface.**Pressure**is the thrust or force applied over a specific area.

## Thrust and Pressure for Class 9

For Class 9 students, understanding the difference between thrust and pressure is important. Let’s look at some examples and numerical problems to make these concepts clearer.

## Atmospheric Pressure

Atmospheric pressure is the thrust or weight of the air exerted on per unit surface area of the earth.

1 atmospheric pressure = 101325 Pa which is equivalent to 760 mm Hg

## The Pressure in a Liquid

The pressure in a point within the liquid depends on how much weight of the liquid is above that point, as the depth increases the number of preceding layers of liquid increases and thus weight of the liquid also enhances, it is that’s why with the depth the pressure of the liquid also increases.

Let the depth of a point in a liquid = h, the density of the liquid is =ρ, gravitational acceleration = g, Weight of the liquid above the point = W, Mass of the liquid above the point = m, Area of the cross-section of the container at the point = A

**Weight of the liquid above the point = mass of the liquid above the point × gravitational acceleration**

W = mg = ρVg

Area of cross-section of the container = A = V/h

**S.I Unit of Pressure **

Pressure = Force/Area = Newton/meter²

1 Newton/meter² = 1 Paskal = 1Pa

## Numerical Questions based on Thrust and Pressure Class 9

**Q1. A cuboidal box of the dimension 20 cm × 15 cm × 10 cm, lying on a table in a position that its largest cross-sectional face is in contact with the table, find the pressure exerted by the box to the table if the mass of the box is 1.2 kg.**

Ans. We are given the dimension 20 cm × 15 cm × 10 cm, The face with largest cross-sectional area = 20cm×15cm

Therefore the pressure exerted by the face, 20cm×15cm to the table is = 392 Pa

**Q2. A cow of the mass 400 kg is stood on a single leg, if the area of its leg is 20 cm², find the pressure exerted by its leg to the ground.**

Ans. Area of the leg, A = 20 cm² = 0.0020 m², mass of the cow, m = 400 kg

Weight = mg = 400 × 9.8 = 3920.0 N

The area exerted by the leg to the ground =1960000 Pa

**Q3. A 3 m height container, sealed, is half-filled by fluid. The density of the fluid is ρ = 1.5 Kg/m ^{3}. What is the pressure at the bottom of the container?**

Ans. Height of the container = H=3m, Depth of the fluid ,h= H/2= 3/2=1.5 m, the density of the fluid is ρ = 1.5 Kg/m^{3}

Pressure = ρhg = 1.5 × 1.5 × 9.8 = 22.05

Therefore Pressure at the bottom =22.05 Pa

**Q4. A 20 m height container is filled with fluid. The container is open. The density of the fluid is ρ = 50 Kg/m ^{3}. What is the pressure at the bottom of the container?**

Ans. Depth of the fluid = 20m, the density of the fluid is ρ = 50 Kg/m^{3}

Gravitational acceleration, g = 9.8 m/s²

Pressure = ρhg = 50 × 20 × 9.8 = 9800 Pa

The pressure exerted by the fluid inside the container at the bottom = 9800 Pa

Since the container is open so atmospheric pressure must also be added applied on top of the container

So, net pressure at the bottom of the container = Atm.pressure + 9800Pa = 101325Pa + 9800Pa= 111125Pa

## Conclusion

Understanding **thrust and pressure** and their differences is crucial for Class 9 students. These concepts are not only important for exams but also for understanding various physical phenomena in daily life. How did you like this post on thrust and pressure? Please write your comments!

## FAQs on the Difference Between Thrust and Pressure for Class 9 Students

Pressure is directly related to thrust. It measures how the thrust is distributed over an area. Essentially, pressure equals thrust divided by the area over which the thrust is applied.

Thrust is the force applied perpendicular to a surface, whereas pressure is the amount of thrust applied per unit area. Thrust acts in a specific direction, while pressure describes how this force is spread across a surface.

In Class 9 physics, thrust refers to the perpendicular force exerted by a surface on a body. Pressure is defined as the thrust exerted per unit area of the surface.

The SI unit of thrust is the Newton (N).

An example of thrust is the buoyant force that lifts an object in a fluid, such as the lift experienced by a balloon due to the pressure difference between the inside and outside of the balloon.

The SI unit of pressure is the Pascal (Pa), which is equivalent to one Newton per square meter (N/m²).

- The pressure exerted by the tires of a car on the road.
- The pressure of water from a showerhead.
- The pressure of your feet on the ground while standing.
- The pressure applied by a knife blade while cutting food.
- The atmospheric pressure felt around us every day.

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