Physics Chapter: Pressure and Buoyancy

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Questions and Answers

What happens to pressure if the area on which the thrust is applied is increased while keeping the thrust constant?

Pressure becomes zero

Pressure remains the same

Pressure increases

Pressure decreases (correct)

How is buoyant force related to an object floating or sinking in a liquid?

Buoyant force is always greater than the object's weight when it sinks

An object sinks when buoyant force is always equal to its weight

Buoyant force is equal to the object's weight when it sinks

An object floats when buoyant force exceeds its weight (correct)

Using the formula for pressure, which of the following correctly indicates how to calculate it?

Pressure = Volume / Mass

Pressure = Thrust / Area (correct)

Pressure = Thrust × Area

Pressure = Area / Thrust

What is the unit of density?

kg/m³ Signup and view all the answers

If an object has a greater mass but the same volume as another object, which statement is true regarding their densities?

The object with greater mass will have a higher density Signup and view all the answers

How does the volume of an object affect its density if the mass remains constant?

Density decreases as volume increases Signup and view all the answers

A cube has a mass of 3 kg and a side length of 5 m. What is the pressure it exerts on a table, considering g = 10 m/s²?

0.5 Pa Signup and view all the answers

In the context of sharp objects like blades, why do they cut easily?

They have a small area of contact Signup and view all the answers

What determines whether an object floats or sinks in a liquid?

The density of the object relative to the liquid Signup and view all the answers

If a cube has a side length of 3 m and a mass of 27 kg, what is its density?

3 kg/m³ Signup and view all the answers

According to Archimedes' principle, what does a body experience when immersed in a fluid?

An upward force equal to the weight of the fluid displaced Signup and view all the answers

What is relative density?

The ratio of the density of a substance to the density of water Signup and view all the answers

What can be inferred if an object sinks in water?

Its density is greater than that of water Signup and view all the answers

If an object has a volume of 500 cm³ and sinks in a liquid with a density of 0.8 gm/cm³, what is the mass of the liquid displaced?

500 g Signup and view all the answers

How do submarines utilize Archimedes’ principle?

By using buoyancy to float or sink Signup and view all the answers

What is the primary purpose of hydrometers as per Archimedes' principle?

To determine the density of liquids Signup and view all the answers

What happens to the gravitational force between two objects if the distance between them is doubled?

The force decreases to a quarter. Signup and view all the answers

What is the value of the universal gravitational constant G?

6.67 x 10^-11 Nm^2/kg^2 Signup and view all the answers

According to Kepler's first law, the orbit of a planet is described as what shape?

Ellipse with the Sun at one of the foci. Signup and view all the answers

What is the formula to calculate the gravitational force between two objects?

F = G(m_1 * m_2)/r^2 Signup and view all the answers

If the mass of one object is increased while keeping the other mass and distance constant, what happens to the gravitational force?

The force increases. Signup and view all the answers

What is the acceleration experienced by an object falling towards the Earth called?

Gravitational acceleration Signup and view all the answers

According to Kepler's third law, what is the relationship between the distance of a planet from the Sun and its orbital period?

Proportional to the cube of the distance. Signup and view all the answers

If two objects with masses 2 kg and 3 kg are 3 m apart, what is the gravitational force between them?

4.44 x 10^-11 N Signup and view all the answers

What is the value of acceleration due to gravity represented by 'g'?

9.8 m/s² Signup and view all the answers

Which equation represents the relationship between force, mass, and acceleration due to gravity?

$F = mg$ Signup and view all the answers

In the equation $g = \frac{GM}{R^2}$, what does 'R' represent?

Radius of Earth Signup and view all the answers

What is the relationship between mass and weight as described in the content?

Weight depends on mass and acceleration due to gravity. Signup and view all the answers

If two objects of different masses are dropped from the same height, how do their accelerations compare?

Both experience the same acceleration. Signup and view all the answers

How does the mass of an object change when it is relocated from Earth to the Moon?

It remains the same. Signup and view all the answers

What unit is used to measure weight?

Newtons (N) Signup and view all the answers

Which of the following equations correctly expresses the relationship defined by Newton's second law of motion and the universal law of gravitation?

$mg = rac{GmM}{R^2}$ Signup and view all the answers

What is the formula to calculate the weight of an object on the Moon based on its weight on Earth?

Weight on the Moon = Weight on Earth / 6 Signup and view all the answers

If an object has a mass of 0.2 kg, what is its weight on Earth?

19.6 N Signup and view all the answers

What would be the value of acceleration due to gravity on the Moon?

1.63 m/s² Signup and view all the answers

Which statement best describes the relationship between thrust and pressure?

Pressure is directly proportional to thrust. Signup and view all the answers

How would the weight of a 60 N object on Earth compare to its weight on the Moon?

10 N Signup and view all the answers

What is the SI unit of pressure?

Pascal (Pa) Signup and view all the answers

If an object's weight on Earth is 30 N, what is its weight on the Moon?

10 N Signup and view all the answers

What happens to pressure if thrust remains constant but area increases?

Pressure decreases. Signup and view all the answers

Study Notes

Pressure

Pressure is inversely proportional to the area on which the thrust is applied.
Increasing the area on which the thrust is applied, while keeping the thrust constant, will decrease pressure.
Applying the same thrust on a smaller area will create larger pressure.
Sharp objects have a small area of contact, resulting in high pressure and making them effective for cutting.

Example Calculation: Pressure of a Cube

A cube with a mass of 2 kg and a side length of 10 m rests on a table.
The area of its base is 100 m².
The cube exerts a force (thrust) on the table equal to its weight, which is 20 N.
The pressure exerted by the cube on the table is 0.2 Pa.

Buoyancy

When an object is immersed in a liquid, it experiences an upward force called buoyant force.
An object floats if the buoyant force is greater than its weight.
An object sinks if its weight is greater than the buoyant force.

Density

Density is defined as the mass per unit volume.
Density is directly proportional to mass: increasing the mass at a constant volume increases density.
Density is inversely proportional to volume: decreasing the volume at a constant mass increases density.
An object floats if its density is less than the density of the fluid it is in.
An object sinks if its density is greater than the density of the fluid it is in.

Example Calculation: Density and Buoyancy of a Cube

A cube with a side length of 2 m and a mass of 16 kg is suspended in a liquid with a density of 3 kg/m³.
The volume of the cube is 8 m³.
The density of the cube is 2 kg/m³.
The cube will float because its density is less than the density of the liquid.

Archimedes Principle

When a body is fully or partially immersed in a fluid, it experiences an upward force equal to the weight of the fluid displaced by it.
This principle has applications in designing ships and submarines, lactometers, and hydrometers.

Example Calculation: Archimedes Principle

An object with a volume of 250 cm³ is submerged in water.
The density of water is 1 g/cm³.
The mass of the water displaced by the object is 250 g (according to Archimedes' principle).

Relative Density

Relative density is the ratio of the density of a substance to the density of water.
It is unitless because it is a ratio of two densities.

Gravitation

Gravitation is the force of attraction between any two objects with mass.
It explains why objects fall to Earth, planets revolve around the sun, and the moon revolves around Earth.

Law of Universal Gravitation

The gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
The formula is F = (Gm₁m₂)/r², where G is the universal gravitational constant, m₁ and m₂ are the masses of the objects, and r is the distance between them.
G = 6.67 × 10⁻¹¹ Nm²/kg².

Example Calculation: Gravitational Force

Two objects with masses of 2 kg and 3 kg are separated by 3 m.
The gravitational force between them is 4.44 × 10⁻¹¹ N.

Kepler's Laws of Planetary Motion

Kepler's First Law: Planets orbit the Sun in elliptical paths with the Sun located at one of the foci of the ellipse.
Kepler's Second Law: The line joining a planet to the Sun sweeps out equal areas in equal intervals of time.
Kepler's Third Law: The square of a planet's orbital period is proportional to the cube of the semi-major axis of its elliptical orbit.

Free Fall and Acceleration Due to Gravity

Acceleration due to gravity (g): The acceleration experienced by an object falling towards Earth due to its gravitational pull.
Its value is 9.8 m/s².
The formula for acceleration due to gravity is g = GM/R², where M is the mass of Earth, R is the radius of Earth, and G is the universal gravitational constant.

Example: Acceleration due to Gravity

A hollow cylinder and a solid cylinder of different masses are dropped from a building. They will experience the same acceleration due to gravity (g) and fall at the same rate.
Acceleration due to gravity is independent of an object's mass.

Mass and Weight

Mass: The amount of matter in a body. It remains constant throughout the universe.
Weight: The force of gravity acting on an object. It is the product of mass and acceleration due to gravity (W = mg).
The unit of weight is Newtons (N).

Example: Mass and Weight

An object with a mass of 200 g on Earth will have a weight of 1.96 N (g = 9.8 m/s²).
The mass of the object will be 200 g regardless of location (Earth, Moon, etc.).

Weight on the Moon

The acceleration due to gravity on the Moon is about 1/6th that of Earth.
An object's weight on the Moon will be 1/6th its weight on Earth.

Example: Weight on the Moon

An object weighing 60 N on Earth will weigh 10 N on the Moon.

Thrust and Pressure

Thrust: The force acting perpendicular to a surface. It is measured in Newtons (N).
Pressure: The force (thrust) acting per unit area. It is measured in Pascals (Pa) or N/m².
Pressure is directly proportional to thrust.
Pressure is inversely proportional to the area over which the force is applied.

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Description

Explore the concepts of pressure, buoyancy, and density in this quiz. Understand how pressure varies with area, the effects of buoyant force on floating objects, and the definition of density. Test your knowledge with calculations and theoretical questions.