Physical Quantities
Scalar Quantities: which have only magnitude and no direction. e.g. mass, speed, volume, distance etc.
Vector Quantities: which have both magnitude and direction. e.g. velocity, displacement, momentum, force etc.
Tensor Quantities: which are neither scalar or vector quantities. e.g. Stress, Inertia etc.
Newton's laws of motion
FIRST LAW: Law of Inertia or Law of Galileo
"Every object will remain at rest or in uniform motion in a straight line, until an external force applied on it."
Definition of Inertia: The virtue of a body due to which it tries to retain its state. or a tendency to do nothing or to remain unchanged.
There are three type of Inertia.
Inertia of 1. of rest 2. of motion 3. of direction.
E.g. If a moving car suddenly stops, the person sitting in falls forward.
E.g. When carpet is beaten with stick the dust particle come out from it due to Inertia of Rest.
SECOND LAW
"The force applied on a body is equal to the product of its mass and acceleration." F=ma
Second law of motion gives the definition of FORCE.
SI unit of FORCE is NEWTON.
THIRD LAW
"for every action there is equal and opposite reaction."
Action and Reaction always act on the different bodies.
Application: Recoiling of Gun, Rocket Propulsion, Bogies of the trains are provided with buffers to avoid severe jerks during shunting of trains.
Linear Momentum
Momentum is a physics term; it refers to the quantity of motion that an object has. If an object is in motion (on the move) then it has momentum. Momentum can be defined as "mass in motion".Linear momentum is a vector quantity defined as product of mass and velocity, denoted by 'p'
p=m*v unit is kg-m/s
A heavy body has the larger linear momentum.
A body's momentum is always in same direction as velocity.
"In the absence of external force, the total linear momentum of the system remain conserved. This is called conservation of linear momentum."
Application: rocket propulsion, recoiling of gun.
Impulse
The force acting on a body for a short period of time is called Impulse. It is the product of Force and Time. Impulse is equal to change in momentum.
Application:
A cricket lower his hand while catching a ball.
Car, bus and all vehicle are provided with Shockers.
Bogies of train are provided with buffers (They increase the time duration of jerks during shunting).
Circular motion
FRICTION
"The resisting force that comes into play when one body moves or tend to move over the other.
Static Friction: comes into the play before the motion starts."
The maximum value of static friction force that comes into play when body just begins to slide over the surface of the other is called limiting frictional force.
Rolling friction comes into play when two bodies roll over each other. e.g. ball bearing.
Slide friction comes into play when two bodies actually slide over one other.
Force of friction acting between two surface contact, when a body is moving over the other body is called Kinetic friction.
Pascals Law of Pressure
Hydraulic lift, hydraulic press and hydraulic brakes are based on the Pascal's law of pressure.
Archimedes' Principle
WORK
ENERGY
The ability to do work is called Energy. Its SI unit is Joule, In CGS system unit is Erg.
Mechanical Energy is of two types.
1. Kinetic Energy: It is due to virtue of motion.
2. Potential Energy: It is due to virtue of its height or configuration or rest.
ENERGY TRANSFORMATION
Heat Engine: Heat energy to Mechanical energy.
Solar Cell: Solar energy to Electrical energy.
Microphone: sound to electrical energy.
Loudspeaker: electrical to sound energy.
Battery: Chemical to Electrical energy.
Candle: Chemical to Light energy.
Electric Motor: Electrical to mechanical energy.
Sitar: Mechanical to sound energy.
Electric Bulb: Electrical to Light energy.
POWER
Scalar Quantities: which have only magnitude and no direction. e.g. mass, speed, volume, distance etc.
Vector Quantities: which have both magnitude and direction. e.g. velocity, displacement, momentum, force etc.
Tensor Quantities: which are neither scalar or vector quantities. e.g. Stress, Inertia etc.
Newton's laws of motion
FIRST LAW: Law of Inertia or Law of Galileo
"Every object will remain at rest or in uniform motion in a straight line, until an external force applied on it."
Definition of Inertia: The virtue of a body due to which it tries to retain its state. or a tendency to do nothing or to remain unchanged.
There are three type of Inertia.
Inertia of 1. of rest 2. of motion 3. of direction.
E.g. If a moving car suddenly stops, the person sitting in falls forward.
E.g. When carpet is beaten with stick the dust particle come out from it due to Inertia of Rest.
SECOND LAW
"The force applied on a body is equal to the product of its mass and acceleration." F=ma
Second law of motion gives the definition of FORCE.
SI unit of FORCE is NEWTON.
THIRD LAW
"for every action there is equal and opposite reaction."
Action and Reaction always act on the different bodies.
Application: Recoiling of Gun, Rocket Propulsion, Bogies of the trains are provided with buffers to avoid severe jerks during shunting of trains.
Linear Momentum
Momentum is a physics term; it refers to the quantity of motion that an object has. If an object is in motion (on the move) then it has momentum. Momentum can be defined as "mass in motion".Linear momentum is a vector quantity defined as product of mass and velocity, denoted by 'p'
p=m*v unit is kg-m/s
A heavy body has the larger linear momentum.
A body's momentum is always in same direction as velocity.
"In the absence of external force, the total linear momentum of the system remain conserved. This is called conservation of linear momentum."
Application: rocket propulsion, recoiling of gun.
Impulse
The force acting on a body for a short period of time is called Impulse. It is the product of Force and Time. Impulse is equal to change in momentum.
Application:
A cricket lower his hand while catching a ball.
Car, bus and all vehicle are provided with Shockers.
Bogies of train are provided with buffers (They increase the time duration of jerks during shunting).
Circular motion
- When an object move along a circular path, its motion called circular motion.
- The external force required to act radially inward over the circular motion of the body is called centripetal force.
- Centrifugal force is such a pseudo force that is equal and opposite to centripetal force.
- Cream separator, centrifugal dryer work on the principal of centrifugal force.
"The resisting force that comes into play when one body moves or tend to move over the other.
Static Friction: comes into the play before the motion starts."
The maximum value of static friction force that comes into play when body just begins to slide over the surface of the other is called limiting frictional force.
Rolling friction comes into play when two bodies roll over each other. e.g. ball bearing.
Slide friction comes into play when two bodies actually slide over one other.
Force of friction acting between two surface contact, when a body is moving over the other body is called Kinetic friction.
Pascals Law of Pressure
Hydraulic lift, hydraulic press and hydraulic brakes are based on the Pascal's law of pressure.
Archimedes' Principle
- When a body is immersed partly or wholly in a liquid, there is an apparent loss in the weight of the body, which is equal to the weight of liquid displaced by the body.
- The weight of water displaced by an iron ball is less than its own weight. Whereas water displaced by the immersed portion of a ship is equal to its weight. So, small iron ball sink in water, but large ship float.
- A fat person will quickly learn swimming as compared to a slim person because he will displace more water. So, it will be more balanced.
- Hydrogen filled balloon float in air because hydrogen is lighter than air. A person can lift more weight in water.
WORK
- The work is said to be done when a force is applied on a body and the body displaces from its initial position. Work is a scalar quantity. Work unit is Joule.
- Positive Work done: When the displacement is in the direction of force applied. e.g. man pulling a box.
- Negative Work done: When displacement is in the opposite direction of force applied (when a positive charge moves towards the other positive charge)
- Zero Work done: If displacement is perpendicular to the force applied, or either of the two is zero. e.g If a person is holding a heavy weight but isn't moving, scientifically, he is not doing any work.
- The sum of all kinds of energies in an isolated system remains constant at all times. This is the law of conservation of energy.
ENERGY
The ability to do work is called Energy. Its SI unit is Joule, In CGS system unit is Erg.
Mechanical Energy is of two types.
1. Kinetic Energy: It is due to virtue of motion.
2. Potential Energy: It is due to virtue of its height or configuration or rest.
ENERGY TRANSFORMATION
Heat Engine: Heat energy to Mechanical energy.
Solar Cell: Solar energy to Electrical energy.
Microphone: sound to electrical energy.
Loudspeaker: electrical to sound energy.
Battery: Chemical to Electrical energy.
Candle: Chemical to Light energy.
Electric Motor: Electrical to mechanical energy.
Sitar: Mechanical to sound energy.
Electric Bulb: Electrical to Light energy.
POWER
- The rate of doing work by a body is called Power. SI unit of work is WATT or JOULE SECOND.
- 1 watt hour = 3600 Joule
- 1 kilowatt hour = 3.6 x 10^6 joule
- 1 HP = 746 watt