The basic equation for thrust is

• A. Thrust = Mass * Acceleration
• B. Thrust = Force * Acceleration
• C. Thrust = Mass * Velocity
• D. Thrust = Velocity * Acceleration

Answer: (A)

Thrust is a force, produced when the engine accelerates mass (the exhaust or intake air). Newton’s second law says that force equals mass times acceleration. So if you take a chunk of exhaust gas with mass m and give it acceleration a as it leaves the nozzle, the engine must push with a force F = m × a, and the engine experiences an equal and opposite thrust. In practice, jet propulsion often uses the more detailed idea that thrust is related to the rate of momentum change (m_dot × V_exit), but the fundamental relation for thrust as a force is still F = m a. The other options mix up fundamental quantities: momentum is mass times velocity, not force; velocity times acceleration or force times acceleration don’t yield a standard thrust quantity with the correct units.