The following factor affects the orbit of a satellite up to an altitude of 720 km from the earth's surface
A. Uneven distribution of the gravitational field
B. Gravity of the sun and the moon
C. Aerodynamic forces
D. None of these
Answer: Option C
Solution (By Examveda Team)
Why: Up to about 720 km altitude, satellites are still in Low Earth Orbit (LEO), where the atmosphere is very thin but not absent. The residual air molecules produce aerodynamic drag on a satellite moving at roughly 7.5 km/s, which continuously removes orbital energy and causes gradual orbital decay.Option A (Uneven gravitational field): Earth’s oblateness and mass irregularities do perturb orbits (e.g., nodal and apsidal precession), but at ~720 km these effects are secondary compared with drag when considering orbit maintenance and decay over practical timescales.
Option B (Gravity of the Sun and Moon): Third-body perturbations exist at all altitudes but are comparatively minor for LEO; their influence becomes relatively more important at higher altitudes (e.g., MEO/GEO).
Option C (Aerodynamic forces): Dominant disturbance in LEO up to ~720 km. Drag reduces velocity, lowers perigee, and accelerates decay, requiring periodic reboosts for orbit maintenance.
Conclusion: At altitudes up to 720 km, aerodynamic drag is the principal factor affecting a satellite’s orbit, making Option C correct.
This Question Belongs to Civil Engineering >> Applied Mechanics And Graphic Statics
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A. $${\text{T}} = \frac{{2\omega }}{{{\pi ^2}}}$$
B. $${\text{T}} = \frac{{2\pi }}{\omega }$$
C. $${\text{T}} = \frac{2}{\omega }$$
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B. 1 rad/sec
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