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GATE 2026 AE – Question 41

Propulsion · Rockets: thrust equation, specific impulse, multi-staging, solid and liquid propellant rockets · 2 marks · Multiple choice

Consider a launch vehicle of mass 10 tons being launched vertically. The vehicle has 8 tons of propellant, which burns completely at a constant rate over 50 s. If the engine specific impulse is 250 s, and the acceleration due to gravity at sea level is $g_0$, the acceleration experienced by the vehicle at lift-off is ________.

  1. $g_0$
  2. $2g_0$
  3. $3g_0$
  4. $4g_0$

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Correct answer: (C) $3g_0$

Explanation

The mass flow rate is $\dot m = \frac{8000}{50} = 160$ kg/s. The thrust is $T = I_{sp} g_0 \dot m = 250 \times 160\, g_0 = 40000\, g_0$ N. At lift-off the net acceleration is $a = \frac{T}{m} - g_0 = \frac{40000 g_0}{10000} - g_0 = 3g_0$.

Official GATE 2026 answer key: https://gate2026.iitg.ac.in/doc/download/2026/Keys/AE_Keys.pdf