Mechanical Properties Of Fluids Class 11 Notes

What is Translational Motion?

Let us understand translational motion with the help of examples. Let’s imagine a rectangular block placed on the slanting edge of a right-angled triangle. If the block is assumed to slide down this edge without any side movement, every point in the rectangular block experiences the same displacement and more importantly, the distance between the points is also maintained.

In a pure translational motion, every point in the body experiences the same velocity be it at any instant of time. Both the points, P1 and P2 undergo the exact same motions. A car moving in a straight line, the path of a bullet out of a gun etc are examples of translational motion.

What is Rotational Motion?

Lets us understand this by an example. Now let us imagine a circular block going down the edge of the right-angled triangle. Examining the location and orientation of different points on the cylindrical block will tell us something new. The points on the cylindrical body experience something much different than the rectangular block. As shown by the arrows in the diagram representing the velocity, each point experiences a different magnitude of velocity in a different direction. Here the points are arranged with respect to an axis of rotation.

Rotation is what you achieve when you constrain a body and fix it along with a straight line. This means that the body can only turn around the line, which is defined as rotational motion. A ceiling fan, a potter’s wheel, a vehicle’s wheel are all examples of rotational motion.
Important Questions
Give the location of the center of mass of a
- (i) sphere,
- (ii) cylinder,
- (iii) ring, and
- (iv) cube, each of uniform mass density.
Does the centre of mass of a body necessarily lie inside the body?
1. Two particles, each of mass m and speed v, travel in opposite directions along parallel lines separated by a distance d. Show that the angular momentum vector of the two-particle system is the same whatever be the point about which the angular momentum is taken.
1. Torques of equal magnitude are applied to a hollow cylinder and a solid sphere, both having the same mass and radius. The cylinder is free to rotate about its standard axis of symmetry and the sphere is free to rotate about an axis passing through its centre. Which of the two will acquire a greater angular speed after a given time?
Students can find details about the system of particles and rotational motion class 11 notes from this article.
Frequently asked Questions on CBSE Class 11 Physics Notes Chapter 7: System of Particles and Rotational Motion
What are some of the examples of ‘torque’ in real life?
Opening a bottle cap or turning a steering wheel are examples of torque.
What is meant by ‘Centre of mass’?
The center of mass is the unique point at the center of a distribution of mass in space that has the property that the weighted position vectors relative to this point sum to zero.
What is meant by ‘Magnitude’?
Magnitude can be described as ‘distance or quantity’. It shows the direction or size that is absolute or relative in which an object moves in the sense of motion.

List of Content

What is Work?

What is Power?

What is Energy?

What is the Principle of Conservation of Energy?

Important Questions

CBSE Class 11 Physics Work-Energy And Power Notes

Work, power, and energy are among the most important concepts of mechanics. A moving car, walking up stairs, lifting heavy objects, an aeroplane flying, etc are among the most common examples that give us insight into the concept of work, power, and energy. There are few common notions of work, power, and energy that can be precisely defined in physics. These notions and measurements can be utilized to define and predict the motion and behavior of bodies.

See Also: Important Questions – Work, Energy and Power

What is Work?

Work is the measurement of energy transfer that takes place when an object is displaced by an external force applied in the direction of the displacement.

What is Power?

The rate of doing work is called power.

What is Energy?

The capacity for doing work is called Energy. It may exist in kinetic, potential, thermal, chemical, electrical, nuclear, or various other forms. The SI unit of energy is the same as that of work.

What is the Principle of Conservation of Energy?

The Principle related to the conservation of mechanical energy states that the total mechanical energy of a substance remains in equilibrium if the only forces acting upon the body are conservative in nature.

Law Of Conservation Of Energy

Energy can neither be created nor be destroyed however, it can be changed from one to another form. The total energy in an isolated system remains the same or energy is conserved over time. The mass remains the same in any closed system within boundaries except for the heat form which can cross boundaries.

As per the law, energy cannot be created and neither can be destructed but conveniently can be changed to different forms. Chemical energy can be converted into heat energy which could further be used to generate potential energy in a different body. As energy is changed from one to another form, net gain/loss remains the same. Therefore, energy is said to be conserved wherein the total amount remains Same

Work Energy And Power Important Questions

The sign of work done by a force on a body is important to understand. State carefully if the following quantities are positive or negative:

(a) work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket.
(b) work done by gravitational force in the above case,
(c) work done by friction on a body sliding down an inclined plane,
(d) work done by an applied force on a body moving on a rough horizontal plane with uniform velocity,
(e) work done by the resistive force of air on a vibrating pendulum in bringing it to rest.

Underline the correct alternative :

(a) When a conservative force does positive work on a body, the potential energy of the body increases/decreases/remains unaltered.
(b) Work done by a body against friction always results in a loss of its kinetic/potential energy.
(c) The rate of change of total momentum of a many-particle system is proportional to the external force/sum of the internal forces on the system.
(d) In an inelastic collision of two bodies, the quantities which do not change after the collision is the total kinetic energy/total linear momentum/total energy of the system of two bodies.

Work Power and Energy Questions Explained, Watch The Below Videos:

These work energy and power class 11 notes pdf can be viewed below:

The students can prepare all the important concepts included in this unit by referring to the work energy and power class 11 notes pdf from the links mentioned below:

Work Energy and Power Class 11 notes pdf
Energy
Work
Types of Energy
Heat Energy and Internal Energy
Different Forms Of Energy
Power
Conventional and Non-conventional Energy Sources
Kinetic Energy
Electric Power
Potential energy

Fequently asked Questions on CBSE Class 11 Physics Notes: Work Energy Power

What is the ‘Law of conservation of energy’?

The law of conservation of energy states that the amount of energy is neither created nor destroyed.

What is ‘Work’?

The measure of energy transfer that occurs when an object is moved over a distance by an external force is known as ‘Work’.

What is the definition of ‘Power’?

Power can be defined as a rate of energy consumption.

Laws Of Motion Class 11 Notes

What is Inertia?

The property of an object by virtue of which it cannot change its state of uniform motion along a straight line or rest on its own is called as inertia. It is the measure of the mass of a body. There are 3 types of inertia.

Inertia of rest
Inertia of motion
Inertia of direction

See Also: Difference between Momentum and Inertia

What is Force?

A force is a push or pull upon an object resulting from the object’s interaction with another object. Force can be categorized into two types;

Constant Force
Action at a distance force

What are Newton’s Laws of Motion?

First Law:“A body continues in its state of rest or of uniform motion in a straight line unless it is compelled by some external force to change that state.”
Second Law:“The net force produced by an object is directly proportional to the magnitude of the net force and takes place in the direction of the force.”
Third Law:“To every action, there is an equal and opposite reaction.”Important Questions

Aristotle observed that the force is mandatory to keep an object in uniform motion is wrong. He found that force is required only to keep the opposing force of friction.
Galileo came to a conclusion about law of inertia with the help of simple observations on the motion of objects on the inclined planes. The statement of Newton’s first law is re-framed as “Everybody continues to be in its state of rest or of uniform motion until and unless an external force acts on it.”
Momentum (p ) of a body is the product of its mass (m) and velocity

Do check out the given links to know more about the topics in detail. Inertia, Force, Laws of Motion, Newton’s First Laws of Motion, Newton’s Second Laws of Motion, Newton’s Third Laws of Motion

Frequently asked Questions on CBSE Class 11 Physics Notes: Laws of Motion

What is ‘Inertia’?

Inertia is a property of matter by which it remains at rest or in motion in the same straight line unless acted upon by some external force.

What are some of the uses of ‘Force’ in real life?

1. Weight things 2. Force of bat on a ball

Why is the third law of motion important?

This law is important in analysing problems of static equilibrium, where all forces are balanced

Class 11 Physics Chapter 3 Notes Motion In A Straight Line

Motion in a Straight Line

A body is said to be in motion if it changes its position with respect to time.

To get more details on Motion in a Straight Line,

Types of Rectilinear/Linear Motion

The Rectilinear Motion or linear motion can be of two types:

Non-Uniform linear motion with non-zero acceleration or variable velocity
Uniform linear motion with zero acceleration or constant velocity

The simplest type of one-dimensional motion is Linear motion. As per Newton’s first law of motion, an object will either be in rest or continue to move in a straight line with a uniform velocity unless and until an external force is applied to it.

Linear motion is often mistaken for general motion. Linear motion is a one-dimensional motion but in general, the motion has both magnitude and direction, i.e. an object’s position and velocity are described in vector quantities.

To get more details on Rectilinear Motion,

Uniform Motion in a Straight Line

Motion in a Straight Line

A body is said to be in a uniform motion if it travels in a straight line covering equal distances in equal intervals of time. A body is said to have uniform acceleration if the rate of change of its velocity remains constant.

The ball covers equal distances in equal intervals of time

Example:

If a car travels at a speed of 60 km/hour then it will cover a distance of 1 km/minute. In this sense, the motion of car acceleration is uniform.

For More Information On Motion in One Dimension, Watch The Below Video:

Non-uniform Motion in a Straight Line

A body is said to have a non-uniform motion when the velocity of a body changes by unequal amounts in equal intervals of time. While in movement, the rate of change of its velocity changes at different points of time.

Example:

A boy kicking a football. It might cover 4 meters in the first attempt, 6 meters in the second change, 9 meters in the third attempt and so on as per the velocity exerted by the boy.

To get more details on Uniform and Non-Uniform Motion,

Path Length

The path length is the total length of the path that has to be traversed by the object.

Displacement

Displacement is the change in position of a body. The magnitude of displacement between the same points is proportional to the path length.

To get more details on Displacement Formula,

Uniform Motion

When the displacement of an object is equal in equal time intervals, the motion is said to be uniform, else it is referred to as non-uniform.

Average Speed

Average speed is referred to the ratio between the total path length traversed to the time taken.

To get more details on Average Speed,

Instantaneous Velocity

It is the velocity when the limit of the average velocity has an indefinitely smaller interval of time.

To get more details on Instantaneous Velocity Formula

Average Acceleration

It is the change in velocity corresponding to the time interval with in which the change has accelerated

What are units and measurements?

Units and measurement which is given in class 11 physics textbook offer basic knowledge about how the quantities are measured and the types of units that are used with them.

To get more details on Standard Measurement Units,

What is the system of units?

Some of the common systems of units that are used in physics are:

CGS system
FPS system
MKS system
SI system

What is known as the fundamental quantity?

Certain quantities have been chosen as fundamental quantities because physics is considered to be quantitative science. They are:

Length
Mass
Time
Electric Current
Thermodynamic Temperature
Amount of Substance
Luminous Intensity

What is SI unit?

The term stands for International System of Units which has regulated seven base units to be used to represent quantity around the world. These units are:

Metre
Kilogram
Second
Ampere
Kelvin
Mole
Candela

Physics is the study of matter, basic principles and laws of nature along with their manifestations. The study of physics is mainly involved in the explanations of the diverse phenomena of its concepts.

Definition of Physical World

The physical world is referred to as the complexity in nature and solving its own complexities will give us new insights into this physical world. It is referred to as the analysis of nature conducted in order to understand how the world around us performs.

What are the Fundamental Forces of nature?

In this diverse world, the fundamental forces which govern the phenomena occurring in it are:

Gravitational Force – it is a universal force that exists which is of mutual attraction between any two objects by virtue of their masses.
Electromagnetic Force – is the force between charged particles. If charges are in a state of rest, it is given by Coulumb’s law whereas when they are in motion, they generate a magnetic field, hence the name electromagnetic forces as they are inseparable. They also act over a large distance as seen in the case of gravitational forces without the intervention of any medium
Strong Nuclear Force – in a nucleus it binds protons and neutrons. It is the strongest of all the fundamental forces and is charge-independent acting between proton-proton, proton-neutron, or neutron-neutron
Weak Nuclear Force – observed only in some nuclear processes. Example – β-decay of a nucleus. It is not as weak as the gravitational force but weaker than electromagnetic and strong nuclear force