Cadet Competition Written Practice Exam

What caused the rotation of the sphere in Hero's engine?

1. Thrust

2. Drag

3. Weight

4. Pressure

The correct answer is: Thrust

The rotation of the sphere in Hero's engine is caused by thrust. In Hero's engine, steam is directed through nozzles that are positioned tangentially to the sphere. As the steam escapes, it creates a force that propels the sphere in the opposite direction, according to Newton's third law of motion. This reaction creates the rotational motion of the sphere as the escaping steam generates a thrust that pushes against the surface of the sphere, causing it to spin. The thrust acts as a driving force that initiates and maintains this rotation, showcasing the principles of force and motion in a practical application of steam power. The other concepts, such as drag, weight, and pressure, do not directly initiate the rotation in this context. While pressure plays a role in creating steam and the mechanical action of the engine, it is the thrust generated by the steam's escape that is fundamentally responsible for the rotational movement of the sphere.