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Q1. Newton invented a new branch of mathematics called
Newton invented calculus (simultaneously with Leibniz) to help solve problems in physics and mathematics, particularly those involving motion and change.
Q2. The law of gravitation is called universal because it applies to
The law is called universal because it applies to all objects in the universe, regardless of their size, mass, or location.
Q3. The value of G was experimentally found by
Henry Cavendish first measured the value of the universal gravitational constant G in 1798 using a sensitive torsion balance experiment.
Q4. Newton also supported his theory with
Newton supported his gravitational theory with rigorous mathematical proofs and derivations, showing that the inverse-square law was consistent with observational data.
Q5. The force between you and your friend is not felt because it is
The gravitational force between two people is extremely small because their masses are very small compared to celestial bodies. This force is too weak to be felt.
Q6. Kepler could not explain planetary motion because he lacked a
Kepler derived the laws of planetary motion from observational data but could not explain why planets moved in that way. He lacked a theory or physical mechanism, which Newton later provided.
Q7. Newton is best known for formulating the
Newton is best known for formulating the Three Laws of Motion, which form the foundation of classical mechanics.
Q8. Newton based his theory on
Newton based his theories on sound scientific reasoning, combining mathematical analysis with experimental and observational data.
Q9. Combining relations gives gravitational force proportional to
By combining Kepler’s third law with Newton’s second law, Newton showed that gravitational force is inversely proportional to the square of the distance (1/r²).
Q10. The inverse-square rule applies to objects
For a uniform sphere, the inverse-square law applies for points outside the sphere. The gravitational force is calculated as if the entire mass is concentrated at the centre.
Q11. The laws governing planetary motion are called
The three laws that describe the motion of planets around the Sun are called Kepler’s laws of planetary motion, formulated by Johannes Kepler.
Q12. The inverse-square law result is known as the
The inverse-square law states that a physical quantity is inversely proportional to the square of the distance. In gravitation, F ∝ 1/r².
Q13. Despite challenges, there was hardly any doubt about its
Newton’s law of gravitation was so well-supported by evidence that there was hardly any doubt about its correctness, even though it faced some challenges.
Q14. Apart from physics, Newton was also a great
Newton was a brilliant mathematician who invented calculus, made contributions to algebra and geometry, and used mathematics extensively in his physics work.
Q15. The SI unit of G is
From F = GMm/d², we get G = Fd²/Mm. The SI unit of G is N·m²/kg² or N m² kg⁻².
Q16. Gravitational force exists between
Gravitational force exists between any two objects that have mass, no matter how small or large they are. It is a universal force.
Q17. Simplicity and elegance are now considered essential for
Simplicity and elegance are considered hallmarks of a good scientific theory. Newton’s theory of gravitation is admired for being simple and elegant.
Q18. The accepted value of G is
The accepted value of the universal gravitational constant G is 6.67 × 10⁻¹¹ N·m²/kg². This was first measured by Henry Cavendish.
Q19. The explanation of planetary motion was given by
Newton provided the physical explanation for planetary motion by showing that it is due to the gravitational force between the Sun and the planets.
Q20. By the 16th century, much data had been collected on the motion of
By the 16th century, astronomers like Tycho Brahe had collected extensive and accurate data on the motion of planets, which Kepler later used to formulate his laws.
Q21. The square of velocity v² is proportional to
From Kepler’s third law, T² ∝ r³. Since v ∝ r/T, we get v² ∝ r²/T² ∝ r²/r³ = 1/r. So v² ∝ 1/r.
Q22. Newton’s synthesis of earlier ideas was
Newton’s synthesis of earlier ideas from Copernicus, Kepler, Galileo, and others was powerful because it unified celestial and terrestrial mechanics under a single framework.
Q23. Newton also formulated the
Newton formulated the universal law of gravitation, which describes the attractive force between any two objects with mass.
Q24. Newton’s success was due to combining observation with
Newton’s success came from combining careful observation with rigorous mathematical analysis. He used mathematics to derive predictions from his theories.
Q25. Cavendish measured G using a
Cavendish used a sensitive torsion balance apparatus to measure the tiny gravitational force between lead spheres, allowing him to calculate G.
Q26. Kepler’s third law relates the orbital period to
Kepler’s third law states that the square of the orbital period (T²) is proportional to the cube of the mean distance (r³) from the Sun. T² ∝ r³.
Q27. Newton’s gravitational theory is admired mainly for being
Newton’s theory of gravitation is admired for its simplicity and elegance. A simple mathematical formula (F = GMm/r²) explains a vast range of phenomena.
Q28. At the time, Newton’s gravitational theory
Newton’s gravitational theory was supported by observations, such as the motion of the Moon and planets. Later, Cavendish’s experiment provided direct experimental verification.
Q29. Newton transformed physical science using
Newton transformed physical science by formulating the Three Laws of Motion and the Universal Law of Gravitation, which together laid the foundation for classical mechanics.
Q30. Newton designed an astronomical telescope to
Newton designed a reflecting telescope to carry out astronomical observations. This telescope used a curved mirror instead of lenses to focus light.
Q31. The law of gravitation applies to bodies whether they are
The universal law of gravitation applies to all bodies, whether they are celestial (stars, planets) or terrestrial (objects on Earth).
Q32. The astronomer who derived laws of planetary motion was
Johannes Kepler derived the three laws of planetary motion from the accurate observational data of Tycho Brahe.
Q33. According to Kepler’s first law, the orbit of a planet is
Kepler’s first law states that every planet moves in an elliptical orbit around the Sun, with the Sun at one focus of the ellipse.
Q34. In Kepler’s first law, the Sun lies at
According to Kepler’s first law, the Sun is located at one of the two foci of the elliptical orbit of a planet.
Q35. Newton also worked on theories of
Newton made significant contributions to optics. He discovered that white light is composed of different colours and built the first reflecting telescope.
Q36. Newton combined the work of Copernicus, Kepler, Galileo, and
Newton synthesized the work of many scientists including Copernicus, Kepler, Galileo, and others to formulate his unified theory of motion and gravitation.
Q37. Using Kepler’s third law, v² is proportional to
From Kepler’s third law T² ∝ r³, and since v = 2πr/T, we get v² ∝ 1/r. The orbital speed decreases with distance.
Q38. Kepler’s second law states that equal areas are swept in
Kepler’s second law states that a line joining a planet and the Sun sweeps out equal areas in equal intervals of time. This means the planet moves faster when closer to the Sun.
Q39. Isaac Newton lived from
Isaac Newton was born on 4 January 1643 (according to the modern calendar) and died on 31 March 1727. He lived from 1642 to 1727.
Q40. The cause of planetary motion is the
The gravitational force between the Sun and the planets is the cause of planetary motion. This force provides the centripetal force needed to keep planets in orbit.
Q41. For circular planetary orbits, the force on a planet is proportional to
For circular motion, the centripetal force is F = mv²/r. For a planet in circular orbit, the gravitational force provides this centripetal force.
Q42. Newton used which Kepler law to derive the inverse-square law?
Newton used Kepler’s third law (T² ∝ r³) along with his own second law of motion to derive the inverse-square law of gravitation.
Q43. If distance becomes 6 times larger, force becomes
Since F ∝ 1/d², if distance becomes 6 times, force becomes 1/6² = 1/36 times the original force.
Q44. According to Kepler’s third law, r³/T² is
Kepler’s third law states that r³/T² is constant for all planets in the solar system. This constant is the same for all planets orbiting the Sun.
Q45. The inverse-square rule means force is proportional to
The inverse-square rule in gravitation means that the force of attraction is inversely proportional to the square of the distance: F ∝ 1/d².
Q46. Newton’s work was central to the scientific revolution of the
Newton’s work was central to the Scientific Revolution of the 17th century. His laws of motion and universal gravitation transformed physics and astronomy.
Q47. Newton used calculus to prove that a sphere behaves as if its mass is
Newton used calculus to prove that for gravitational purposes, a uniform sphere behaves as if all its mass is concentrated at its centre. This is a key result for applying the law of gravitation to planets and stars.
Q48. Henry Cavendish lived between
Henry Cavendish, the scientist who first measured the value of G, lived from 1731 to 1810. He conducted his famous experiment in 1798.
Q49. The gravitational force between two objects is always
Gravitational force between two objects is always attractive. It pulls objects towards each other and is never repulsive.
Q50. Newton’s law of gravitation was inspired by
According to popular legend, Newton was inspired to study gravity when he saw an apple falling from a tree. This led him to think about why the apple falls downward and why the Moon does not fall to Earth.