🔍 Key Concepts

• Role of crankshaft counterweights in rotating machinery • Difference between centrifugal forces of rotating parts and inertia forces of reciprocating parts • How engine designers achieve dynamic balance in multi‑cylinder high‑speed diesels

💭 Think About

• Think about which parts of the crank/rod/piston assembly are rotating versus which parts move back and forth, and which of these the counterweights can directly offset • Ask yourself: when a crankpin and part of a connecting rod rotate, what kind of force do they create, and how can a weight directly opposite them help? • Consider which option describes balancing of forces during rotation of the crankshaft itself, not the end result on the whole engine structure

✅ Before You Answer

• Identify which answer choice explicitly mentions centrifugal force during rotation • Eliminate any options that describe effects the counterweights cannot directly prevent, such as completely removing bearing loads or all inertia forces • Check which choice matches the idea of balancing the rotating masses on the crankshaft rather than the rocking of the entire engine on its mounts