Physics

Physics

Problem

A boat of mass 200 kg200\,\text{kg} experiences a water resistance of 40 N40\,\text{N} opposite to its motion. The rower pushes the water backward with an average force of 250 N250\,\text{N}. Determine the acceleration of the boat at that instant.
Intuitive explanation

The key is recognizing that net force determines acceleration, not just the applied force. The rower pushes the boat forward with 250 N, but water resistance simultaneously pulls backward with 40 N—you must combine these as vectors (same line, opposite directions) to find the true net force. Once you have the net force, Newton's second law Fnet=maF_{\text{net}} = ma gives you acceleration directly.

Intuitive explanation

The key is recognizing that net force determines acceleration, not just the applied force. The rower pushes the boat forward with 250 N, but water resistance simultaneously pulls backward with 40 N—you must combine these as vectors (same line, opposite directions) to find the true net force. Once you have the net force, Newton's second law Fnet=maF_{\text{net}} = ma gives you acceleration directly.

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