5 Questions
In what shape do planets revolve around the sun according to Kepler's first law?
The planets revolve around the sun in an elliptical orbit with the sun at one of the foci of the ellipse.
What does Newton's law of gravitation state?
Newton's law of gravitation states that 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.
What are the important characteristics of gravitational force?
The important characteristics of gravitational force include: (i) Gravitational force is a central force, acting along the line joining the centres of the two interacting bodies. (ii) It is independent of the nature of the intervening medium. (iii) It does not depend upon the presence of other bodies. (iv) It is valid for point objects and spherically symmetrical objects. (v) The magnitude of the force is extremely small.
What is the universal constant of gravitation, G?
The universal constant of gravitation, G, is numerically equal to the force of attraction between two particles of unit mass each separated by unit distance.
According to Kepler's second law, how does the speed of a planet vary?
The speed of a planet varies in such a way that the radius vector drawn from the sun to the planet sweeps out equal areas in equal times.
Study Notes
Kepler's First Law
- Planets revolve around the sun in elliptical orbits, meaning their orbits are oval-shaped and not circular.
Newton's Law of Gravitation
- The law states that every point mass attracts every other point mass by a force acting along the line intersecting both points, with a magnitude proportional to the product of the two masses and inversely proportional to the square of the distance between them.
Characteristics of Gravitational Force
- Gravitational force is a universal force, as it is always attractive and never repulsive.
- It is a weak force, but can be significant when the masses of objects are large.
- Gravitational force acts over long distances, even across vast distances in space.
Universal Constant of Gravitation (G)
- The universal constant of gravitation, G, is 6.67408e-11 N·m²·kg⁻², representing the strength of gravitational attraction between objects.
Kepler's Second Law
- The speed of a planet varies as it orbits the sun, with the planet moving faster when it is closer to the sun and slower when it is farther away.
Test your knowledge of Kepler's Laws of Planetary Motion and Newton's Law of Gravitation with this quiz. See how well you understand the motion of planets and the force of gravity.
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