Class 11 Physics - WEST-BENGAL
Gravitation
The chapter Gravitation in Class 11 Physics under the West Bengal Council of Higher Secondary Education (WBBSE) introduces students to the fundamental force of attraction between any two objects in the universe. It covers Newton's Law of Gravitation, acceleration due to gravity (g) and its variation with height, depth, and shape of the Earth. Students also learn about gravitational potential energy, escape velocity, and the motion of satellites including Kepler's laws of planetary motion. Mastering this chapter is crucial for board exams as it forms the foundational mechanics for astrophysics and frequently features numerical problems.
Start Learning FreeKey Concepts
Newton's Law of Gravitation
Every particle in the universe attracts every other particle with a force directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
Acceleration Due to Gravity (g)
The uniform acceleration produced in a freely falling body due to the gravitational pull of the Earth, whose value changes with altitude, depth, and latitude.
Gravitational Potential Energy
The work done in bringing a body from infinity to a particular point in a gravitational field, conventionally taken as negative.
Escape Velocity
The minimum velocity required for an object to break free from the gravitational pull of a celestial body and never return to it.
Kepler's Laws of Planetary Motion
Three empirical laws describing the motion of planets around the Sun, focusing on orbits (ellipses), areal velocity, and the time period-radius relation.
Important Formulas
Board Exam Info
In the WBBSE Class 11 Physics exams, the Gravitation chapter typically carries around 5 to 7 marks. Questions usually include a mix of conceptual short answers on the variation of 'g', derivations for escape velocity or orbital velocity, and numerical problems based on Newton's law or Kepler's laws.
Frequently Asked Questions
Why is gravitational potential energy always negative?
It is negative because the reference point (infinity) is chosen where potential energy is zero, and as an object moves closer to the Earth, work is done by the gravitational field, reducing the energy below zero.
Does the acceleration due to gravity remain the same everywhere on Earth?
No, 'g' varies because the Earth is not a perfect sphere (it bulges at the equator), and due to the Earth's rotation, altitude above sea level, and depth below the surface.
What is the difference between orbital velocity and escape velocity?
Orbital velocity is the speed required by a satellite to maintain a stable orbit around a planet, whereas escape velocity is the higher speed needed to escape the planet's gravitational field completely.
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