Physics · Gravitation · NEET
It is always attractive. Any two masses pull each other toward one another along the straight line joining their centres. Gravity has no repulsive form, unlike electric charges. So in NEET problems the direction is always along the line joining the two bodies, pointing inward.
Because the same formula F = G m1 m2 / r squared works everywhere and for everything — an apple and Earth, Earth and Moon, Sun and a planet, or two stars. The constant G has the same value in the whole universe. That universal reach is why NEET treats it as a single master law for the full Gravitation chapter.
No. Unlike electric force, gravitational force does not change if you put air, water, glass, or vacuum between the masses. Only the two masses and the distance between their centres matter. This is a common one-line NEET fact, so remember: medium has no effect on gravity.
The force becomes one-fourth. Because F is proportional to 1 / r squared, if r becomes 2r then r squared becomes 4 r squared, so F drops to F/4. If distance triples, force becomes F/9. NEET loves this inverse-square scaling, so always square the distance ratio.
Yes, equal in size and opposite in direction (Newton's third law). Earth pulls you with the same force you pull Earth. You accelerate a lot because your mass is tiny (a = F/m), while Earth barely moves because its mass is huge. Equal force, very different acceleration.
If the mass of the Sun were ten times smaller and the universal gravitational constant G ten times larger, which statement is NOT correct?
Try the real previous-year questions from this chapter — each with the answer and a full solution.
G is the universal gravitational constant. Its value is 6.67 x 10 to the power minus 11 and its SI unit is N m squared / kg squared. It is a fixed constant, the same everywhere in the universe.
Yes. For spheres like planets, we use the distance r between their centres. So Earth and Moon obey F = G m1 m2 / r squared with r as the centre-to-centre distance.
G is the universal constant (6.67 x 10 to the minus 11, same everywhere). g is the acceleration due to gravity on a planet's surface (about 9.8 m/s squared on Earth) and changes from planet to planet. They are linked by g = G M / R squared.
Because the masses are tiny and G is extremely small. Two 60 kg people 1 m apart feel a force of only about 2 x 10 to the minus 7 N — far too weak to notice. Gravity becomes strong only when at least one mass is planet-sized.
