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Q1. Gravitational force is inversely proportional to
According to the universal law of gravitation, gravitational force is inversely proportional to the square of the distance between the centres of two objects. F ∝ 1/d².
Q2. The relation F × d² = G × M × m is obtained by
From F = GMm/d², we multiply both sides by d² to get F × d² = G × M × m. This is obtained by cross multiplication.
Q3. The distance between the centres of two objects is denoted by
In the universal law of gravitation formula F = GMm/d², the distance between the centres of the two objects is denoted by ‘d’.
Q4. Gravitational force between two objects acts
Gravitational force between two objects acts along the line joining their centres. It is always attractive and directed towards the other object.
Q5. Newton studied at
Isaac Newton studied at Trinity College, Cambridge University. He later became a professor there as well.
Q6. During the plague year, Newton
During the plague year (1665-1666), Cambridge University was closed. Newton returned to his family home in Woolsthorpe and spent the time developing his ideas on calculus, optics, and gravitation.
Q7. Newton belonged to a
Isaac Newton was born into a farming family in Woolsthorpe, England. His father was a farmer who died before Newton was born.
Q8. The strength of gravitational force depends on
Gravitational force depends on the masses of the objects and the distance between them. It does not depend on shape, color, or volume.
Q9. Without centripetal force, the moon would move in
According to Newton’s First Law, without centripetal force, the moon would move in a straight line tangential to its orbit. The gravitational force provides the centripetal force needed for circular motion.
Q10. All planets in the solar system revolve around
All planets in our solar system revolve around the Sun due to the Sun’s gravitational pull. The Sun is at the centre of the solar system.
Q11. The gravitational force is proportional to
Gravitational force is directly proportional to the product of the masses of the two objects. F ∝ M × m.
Q12. If both masses are doubled, gravitational force becomes
F ∝ M × m. If both masses are doubled, new force F’ ∝ (2M)(2m) = 4Mm. So the force becomes 4 times the original.
Q13. The mass of an apple compared to the earth is
The mass of an apple is negligible compared to the mass of the Earth. That’s why we don’t notice the Earth moving towards the apple.
Q14. The force of attraction between objects is called
The force of attraction between any two objects in the universe is called gravitational force. It is a universal force that acts between all objects with mass.
Q15. The universal gravitational constant is represented by
The universal gravitational constant is represented by the symbol ‘G’. Its value is 6.67 × 10⁻¹¹ N·m²/kg².
Q16. According to the universal law of gravitation, every object attracts
According to Newton’s universal law of gravitation, every object in the universe attracts every other object with a force proportional to the product of their masses and inversely proportional to the square of the distance between them.
Q17. If distance between two masses increases, gravitational force
Gravitational force is inversely proportional to the square of distance (F ∝ 1/d²). So when distance increases, gravitational force decreases.
Q18. The plague broke out in Cambridge in
The Great Plague of London broke out in 1665. Cambridge University was closed, and Newton returned to his family home.
Q19. The force that keeps planets in orbit is
Gravitational force between the Sun and planets provides the centripetal force needed to keep planets in their orbits around the Sun.
Q20. We do not see the earth moving towards the apple because
According to Newton’s Third Law, the apple attracts the Earth with the same force as the Earth attracts the apple. But due to the Earth’s huge mass, its acceleration is negligible and not noticeable.
Q21. The direction of gravitational force is along the line joining
Gravitational force acts along the line joining the centres of the two objects. This is true for uniform spherical objects.
Q22. The motion of the moon around the earth is due to
The gravitational force between the Earth and the moon provides the centripetal force required for the moon’s circular motion around the Earth.
Q23. A falling apple moves toward the earth due to
An apple falls towards the Earth due to the gravitational force exerted by the Earth on the apple.
Q24. According to Newton’s third law, the apple
According to Newton’s Third Law, if the Earth attracts the apple, the apple also attracts the Earth with an equal and opposite force. Both objects attract each other.
Q25. The universal law of gravitation was proposed by
The universal law of gravitation was proposed by Sir Isaac Newton in 1687 in his work “Principia Mathematica.”
Q26. Gravitational force exists between
Gravitational force exists between any two objects that have mass, regardless of their size. It is a universal force.
Q27. The straight-line path followed by the stone after release is
When a stone tied to a string is whirled and then released, it flies off along the tangent to the circle at the point of release, due to inertia.
Q28. If there were no gravitational force, planets would move in
Without gravitational force, there would be no centripetal force. Planets would move in straight lines according to Newton’s First Law.
Q29. The constant of proportionality in gravitation is called
The constant of proportionality in the universal law of gravitation is the universal gravitational constant, denoted by G.
Q30. The falling apple incident inspired Newton to study
The famous falling apple incident inspired Newton to think about gravity and led to his formulation of the universal law of gravitation.
Q31. The formula of universal gravitation is
The universal law of gravitation states F = G × M × m / d², where F is gravitational force, G is universal gravitational constant, M and m are masses, and d is distance between centres.
Q32. The gravitational force between two uniform objects acts
For uniform spherical objects, the gravitational force acts as if all the mass is concentrated at the centre. The force acts along the line joining their centres.
Q33. A straight line that meets a circle at only one point is called
A tangent is a straight line that touches a circle at exactly one point. This is the line along which an object moves when released from circular motion.
Q34. The motion of moon is an example of
The moon moves around the Earth in a nearly circular orbit. This is an example of circular motion.
Q35. When a stone tied to a string is whirled and the string breaks, the stone moves along
When the string breaks, the centripetal force is removed. The stone moves in a straight line tangent to the circle at the point of release, due to inertia.
Q36. Newton was born near
Isaac Newton was born in Woolsthorpe-by-Colsterworth, a village near Grantham in Lincolnshire, England.
Q37. In the given example, line ABC is a tangent at point
In a typical tangent diagram, the tangent touches the circle at point B. The line ABC touches the circle at only one point, which is B.
Q38. According to the second law of motion, acceleration is
According to Newton’s Second Law, a = F/m. For constant force, acceleration is inversely proportional to mass.
Q39. The force between the Sun and the planets is
The force between the Sun and the planets is the gravitational force of attraction. This force keeps the planets in their orbits.
Q40. The universal law of gravitation explains
The universal law of gravitation explains the attraction between all objects in the universe, not just falling objects or planetary motion.
Q41. Many scientists before Newton
Scientists before Newton knew about gravity but could not explain why objects fell or why planets moved. Newton provided the mathematical explanation.
Q42. In the formula of gravitation, M and m represent
In the formula F = GMm/d², M and m represent the masses of the two objects between which the gravitational force acts.
Q43. Newton tried to connect gravity with
Newton extended his ideas about gravity by comparing the acceleration of a falling apple (near Earth’s surface) with the acceleration of the Moon in its orbit. This helped him formulate the universal law of gravitation.
Q44. Isaac Newton was born in
Isaac Newton was born at Woolsthorpe Manor, near Grantham in Lincolnshire, England, on 4 January 1643 (according to the Julian calendar then in use).
Q45. The same argument explains why the earth does not move noticeably towards
The same argument about the apple and Earth explains why the Earth does not move noticeably towards the Moon. The Earth’s mass is so large that its acceleration due to the Moon’s attraction is negligible.
Q46. A tangent to a circle touches the circle at
A tangent is a straight line that touches a circle at exactly one point. This is the defining property of a tangent.
Q47. Newton concluded that all objects in the universe
Newton concluded that all objects in the universe attract each other with a force called gravitational force. This led to the universal law of gravitation.
Q48. The centripetal force acting on the moon is provided by
The centripetal force required for the moon’s circular motion is provided by the Earth’s gravitational attraction on the moon.
Q49. Gravitational force between two objects is
Gravitational force is always attractive. It pulls objects towards each other and never repels them.
Q50. The universal law of gravitation is applicable to
The universal law of gravitation is applicable to the entire universe. It governs the motion of all objects, from planets to stars to galaxies.