A rocket moves forward by pushing the surrounding air backwards.
Answer: False
Or read the worked solution below. Jump to the steps ↓
Written solution
Step 1: Analyze the given statement.
The statement asserts that a rocket moves forward by pushing the surrounding air backwards.
Step 2: Examine the propulsion mechanism.
The rocket engine expels its own exhaust gas backward at speed , which is carried aboard as propellant rather than taken from the surrounding air.
Step 3: Apply Newton's Third Law.
The action of expelling gas backward produces an equal and opposite reaction force that pushes the rocket forward.
Step 4: Apply conservation of momentum.
The total momentum of the rocket and the exhaust gas remains conserved.
Step 5: Express the thrust force.
The thrust force is determined by the mass flow rate and the exhaust velocity.
This formula contains no term for the surrounding air, showing that thrust is independent of the atmosphere.
Step 6: Calculate acceleration for a sample case.
For a mass flow rate of , exhaust speed of , and rocket mass of , we find the thrust and acceleration.
Step 7: Evaluate the requirement of air.
Since the propellant is carried entirely on board, the rocket does not require surrounding air and can operate in a vacuum.
Answer: The statement is False. A rocket moves forward by expelling its own propellant backward (in accordance with Newton's third law), and its propulsion is entirely independent of the surrounding air.