Universal Law of Gravitation — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Universal Law of Gravitation MCQs with step-by-step solutions (10 questions). Part of Gravitation & Pressure. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Universal Law of Gravitation · medium · theory
According to Newton's universal law of gravitation, the force between two masses is:
A. directly proportional to the distance between them
B. independent of the distance between them
C. directly proportional to the product of the masses and inversely proportional to the square of the distance ✓ Correct
D. inversely proportional to the product of the masses
Solution: $F = \dfrac{G m_1 m_2}{r^2}$ — proportional to $m_1 m_2$ and inversely proportional to $r^2$.
Q2 — Universal Law of Gravitation · hard · numerical
If the distance between two bodies is doubled, the gravitational force between them becomes:
A. double
B. one-fourth ✓ Correct
C. one-half
D. four times
Solution: Since $F \propto \dfrac{1}{r^2}$, doubling $r$ makes $F$ become $\dfrac{1}{2^2} = \dfrac{1}{4}$ of the original.
Q3 — Universal Law of Gravitation · hard · numerical
If both masses are doubled while the distance between them is kept the same, the gravitational force becomes:
A. 2 times
B. unchanged
C. 4 times ✓ Correct
D. half
Solution: $F \propto m_1 m_2$; doubling both masses multiplies the force by $2 \times 2 = 4$.
Q4 — Universal Law of Gravitation · medium · theory
We do not notice the gravitational force of attraction between everyday objects because:
A. gravity acts only on large planets
B. friction cancels gravity
C. the gravitational constant G is extremely small ✓ Correct
D. small objects have no mass
Solution: G $\approx 6.67\times10^{-11}$ is so tiny that the force between ordinary masses is negligible.
Q5 — Universal Law of Gravitation · medium · theory
The gravitational force between two bodies is always:
A. repulsive
B. zero
C. sometimes attractive, sometimes repulsive
D. attractive ✓ Correct
Solution: Gravitation is always an attractive force between masses.
Q6 — Universal Law of Gravitation · hard · numerical
If the distance between two masses is reduced to half, the gravitational force becomes:
A. 2 times
B. 4 times ✓ Correct
C. one-fourth
D. half
Solution: $F \propto \dfrac{1}{r^2}$; halving $r$ multiplies the force by $\dfrac{1}{(1/2)^2} = 4$.
Q7 — Universal Law of Gravitation · easy · theory
According to the universal law of gravitation, if the distance between two objects is doubled while their masses stay the same, the gravitational force between them becomes:
A. 1/2 of the original force
B. 4 times the original force
C. 2 times the original force
D. 1/4 of the original force ✓ Correct
Solution: Force is proportional to 1/r². When r is doubled, the force becomes 1/(2²) = 1/4 of the original value.
Q8 — Universal Law of Gravitation · medium · numerical
Two objects, each of mass 100 kg, are placed 1 m apart. Taking G = 6.67×10⁻¹¹ N m²/kg², the gravitational force between them is about:
A. 6.67×10⁻⁵ N
B. 6.67×10⁻¹¹ N
C. 6.67×10⁻⁹ N
D. 6.67×10⁻⁷ N ✓ Correct
Solution: F = G m1 m2 / r² = 6.67×10⁻¹¹ × 100 × 100 / 1² = 6.67×10⁻¹¹ × 10000 = 6.67×10⁻⁷ N.
Q9 — Universal Law of Gravitation · medium · theory
The gravitational force between two bodies is F. If both masses are doubled and the distance between them is also doubled, the new force is:
A. becomes four times
B. remains the same ✓ Correct
C. becomes double
D. becomes half
Solution: F is proportional to (m1 × m2) / r². Doubling both masses multiplies the top by 4, and doubling the distance divides by 2² = 4, so the force stays unchanged.
Q10 — Universal Law of Gravitation · hard · numerical
The gravitational force between two masses is F. If one of the masses is tripled and the distance between them is halved, the new force is:
A. 12F ✓ Correct
B. 1.5F
C. 6F
D. 3F
Solution: F is proportional to m/r². Tripling a mass multiplies the force by 3, and halving the distance multiplies it by 2² = 4. Net factor = 3 × 4 = 12, so the new force is 12F.