**Thrust and Pressure**

## Thrust and Pressure

**Thrust and Pressure-** **Thrust and the pressure** both of these quantities you will have studied in your earlier classes. Somehow many of the students confuse while defining **pressure**. Is **pressure** a **force** on per unit area or **thrust** on per unit area? Actually both definitions of **pressure** is correct. **Thrust and force** both are the same things but there is a slight difference between **thrust and force**, actually, **thrust** is directed to a particular direction and it is a reactive **force** caused by the surroundings. As an example, if you push and pull a thing then here it is better to use the world** force**. Actually the term **thrus**t is originated from Newton’s third law,in short **thrust** is the reaction against a **force**. A balloon is lifted up to the sky because of a **thrust** developed due to the **pressure** difference between the air inside the balloon and the air above it.

**NCERT Solutions Class 10 Science from chapter 1 to 16**

**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 thrus**t 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.

**Class 9 science NCERT solutions of chapter 2 -Is matter around us pure?**

**Pressure**

** ** T**hrust** or force per unit area is known as **pressure**

**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

**Class 10 maths ncert solutions chapter 1: Real numbers**

**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 **pressure and thrust.**

**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

**Science and Maths NCERT solution for Class 9 to 11 class**

**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, Depth of the fluid = 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

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

**Study the following important topics also**

**Archimedes Principle: Complete detail**

**Average Speed and Average velocity**

**The second law of motion**

**The universal law of gravitational force**

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