Variation in g — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Variation in g 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 — Variation in g · medium · theory
As we go higher above the surface of the Earth, the value of acceleration due to gravity (g):
A. remains constant
B. increases
C. becomes zero immediately
D. decreases ✓ Correct
Solution: Since $g = \dfrac{GM}{r^2}$, increasing the distance $r$ from the centre decreases $g$.
Q2 — Variation in g · hard · theory
The value of g is greatest at the:
A. top of a mountain
B. poles ✓ Correct
C. centre of the Earth
D. equator
Solution: The Earth is slightly flattened, so the poles are closer to the centre, giving a larger g than at the equator.
Q3 — Variation in g · medium · numerical
The acceleration due to gravity on the Moon is about one-sixth of that on Earth. A body weighing 60 N on Earth weighs on the Moon about:
A. 10 N ✓ Correct
B. 60 N
C. 360 N
D. 6 N
Solution: Weight on Moon $= \dfrac{60}{6} = 10$ N.
Q4 — Variation in g · hard · theory
The value of acceleration due to gravity at the centre of the Earth is:
A. maximum
B. zero ✓ Correct
C. equal to that at the surface
D. infinite
Solution: At the centre the mass pulls equally in all directions, so the net gravitational acceleration is zero.
Q5 — Variation in g · medium · theory
Two bodies of different masses are dropped together from the same height (ignoring air resistance). They:
A. the lighter one reaches first
B. reach the ground at the same time ✓ Correct
C. never reach together
D. the heavier one reaches first
Solution: g is independent of the mass of the falling body, so both accelerate equally and land together.
Q6 — Variation in g · medium · theory
The acceleration due to gravity g on a planet is given by:
A. $g = \dfrac{GM}{R}$
B. $g = GMR^2$
C. $g = \dfrac{GR}{M^2}$
D. $g = \dfrac{GM}{R^2}$ ✓ Correct
Solution: $g = \dfrac{GM}{R^2}$, where M and R are the planet's mass and radius.
Q7 — Variation in g · easy · theory
The value of acceleration due to gravity, g, on the Earth is maximum at:
A. the centre of the Earth
B. the poles ✓ Correct
C. the equator
D. the top of a tall mountain
Solution: The Earth is slightly flattened at the poles, so the polar radius is smallest. Since g is proportional to 1/R², g is largest at the poles.
Q8 — Variation in g · medium · theory
As we go deeper and deeper below the surface of the Earth, the value of g:
A. decreases and becomes zero at the centre ✓ Correct
B. becomes infinite at the centre
C. increases continuously
D. remains constant everywhere
Solution: Below the surface only the mass in the inner sphere pulls the body, so g decreases with depth and becomes zero at the centre of the Earth.
Q9 — Variation in g · hard · numerical
On the surface of the Earth g = 9.8 m/s². At a height equal to the radius of the Earth (h = R), the value of g becomes:
A. 4.9 m/s²
B. 9.8 m/s²
C. 1.225 m/s²
D. 2.45 m/s² ✓ Correct
Solution: g at height h is g R²/(R+h)². With h = R this is g R²/(2R)² = g/4 = 9.8/4 = 2.45 m/s².
Q10 — Variation in g · hard · numerical
A planet has twice the mass of the Earth and twice its radius. The acceleration due to gravity on the surface of this planet is:
A. one-fourth of g on Earth
B. equal to g on Earth
C. twice g on Earth
D. half of g on Earth ✓ Correct
Solution: g is proportional to M/R². Here M is 2 times and R² is 2² = 4 times, so g is 2/4 = 1/2, that is half of g on Earth.