Solar System Dynamics — Homi Bhabha Class 9 Physics MCQs with Solutions
Free Homi Bhabha Class 9 Physics Solar System Dynamics MCQs with step-by-step solutions (10 questions). Part of Observing Space / Astronomy. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Solar System Dynamics · medium · theory
The planets revolve around the Sun in orbits that are:
A. square
B. elliptical ✓ Correct
C. perfectly circular
D. straight lines
Solution: As described by Kepler, planetary orbits are ellipses with the Sun at one focus.
Q2 — Solar System Dynamics · medium · theory
The planet nearest to the Sun is:
A. Earth
B. Mars
C. Mercury ✓ Correct
D. Venus
Solution: Mercury is the innermost planet of the solar system.
Q3 — Solar System Dynamics · medium · theory
The largest planet in the solar system is:
A. Earth
B. Jupiter ✓ Correct
C. Neptune
D. Saturn
Solution: Jupiter is the biggest planet by both diameter and mass.
Q4 — Solar System Dynamics · hard · theory
The asteroid belt of the solar system lies mainly between the orbits of:
A. Earth and Mars
B. Jupiter and Saturn
C. Mars and Jupiter ✓ Correct
D. Venus and Earth
Solution: The main asteroid belt is located between Mars and Jupiter.
Q5 — Solar System Dynamics · hard · theory
A planet closer to the Sun completes one revolution in a shorter time than a distant planet. Therefore, the planet with the shortest year is:
A. Saturn
B. Jupiter
C. Mercury ✓ Correct
D. Neptune
Solution: Being closest, Mercury moves fastest and has the shortest orbital period (year).
Q6 — Solar System Dynamics · medium · theory
The terrestrial (rocky) inner planets of the solar system are:
A. Mercury, Venus, Earth and Mars ✓ Correct
B. Venus, Jupiter, Earth and Neptune
C. Earth, Jupiter, Saturn and Mars
D. Jupiter, Saturn, Uranus and Neptune
Solution: The four inner planets — Mercury, Venus, Earth, Mars — are small and rocky (terrestrial).
Q7 — Solar System Dynamics · easy · theory
According to Kepler, the planets travel around the Sun in orbits that are:
A. Square-shaped loops
B. Straight lines
C. Ellipses with the Sun at one focus ✓ Correct
D. Perfect circles centred exactly on the Sun
Solution: Kepler's first law states that each planet moves in an ellipse with the Sun located at one of the two foci, not at the centre. Circular orbits are only an approximation.
Q8 — Solar System Dynamics · medium · numerical
A hypothetical planet orbits the Sun at a distance of 4 AU. Using Kepler's third law (T squared is proportional to a cubed, with T in years and a in AU), its orbital period is about:
A. 8 years ✓ Correct
B. 64 years
C. 16 years
D. 4 years
Solution: With a = 4, a cubed = 64, so T squared = 64 and T = 8 years. The cube of the distance equals the square of the period when using AU and years.
Q9 — Solar System Dynamics · hard · numerical
Planet A orbits the Sun at twice the distance of Planet B. By Kepler's third law, Planet A's orbital period is longer than Planet B's by a factor of about:
A. exactly 4
B. exactly 2
C. about 2.8 ✓ Correct
D. exactly 8
Solution: Period scales as distance to the power 3/2. Doubling the distance gives a factor of 2 to the power 1.5 = 2 times √2, which is about 2.83.
Q10 — Solar System Dynamics · hard · theory
A comet moves fastest when it is nearest the Sun and slowest when it is far away. This speeding up and slowing down is a direct consequence of:
A. Air resistance acting on the comet in space
B. Conservation of angular momentum, so the comet sweeps out equal areas in equal times ✓ Correct
C. The Sun heating the comet and pushing it faster
D. The comet steadily losing mass as it travels
Solution: This is Kepler's second law (the law of equal areas), which follows from conservation of angular momentum. To sweep equal areas in equal times, the comet must move faster when the Sun is closer.