A 300 kg test object moving at 0.4 m/s is brought to rest without rebound. The current design stops it in 0.2 s; a larger dock fender stops it in 0.8 s. Consider only the contact force along the horizontal direction and use average force = momentum change / stopping time. The proposed design reduces average contact force for a slow approach, but occupies water space and requires inspection. Evaluate adoption for boat users and people accessing the dock, using both a force calculation and wider implications. Evidence limitation: Waves and rebound change momentum differently from the no-rebound laboratory model.

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Momentum-change magnitude 120 kg m/s; average force falls from 600 N to 150 N. A conditional, tested adoption is defensible; average force alone does not establish complete safety or best value. The same test mass loses the same speed in both designs, so the impulse magnitude is 300 × 0.4 = 120 kg m/s. The longer stopping time changes the force, not the total required momentum change. The original average force is 120/0.2 = 600 N and the proposed force is 120/0.8 = 150 N. Both act opposite the initial motion. Relate the calculation to the specific benefit: a larger dock fender reduces average contact force for a slow approach. The smaller average contact force is evidence for improved performance under this test, not a claim that energy or momentum disappears. Balance that benefit against a practical consequence: the design occupies water space and requires inspection. Include the needs of boat users and people accessing the dock, rather than allowing the cheapest purchase price or lowest force alone to decide. A justified recommendation is a monitored trial with a stated acceptance test before broad adoption. Waves and rebound change momentum differently from the no-rebound laboratory model. Report peak force, durability and relevant access constraints alongside the average-force calculation.

Small craft at a shared dock

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