A 80 kg test object moving at 0.5 m/s is brought to rest without rebound. The current design stops it in 0.1 s; a progressive stopping mechanism stops it in 0.25 s. Consider only the contact force along the horizontal direction and use average force = momentum change / stopping time. The proposed design reduces average deceleration in the stated trial, but increases stopping distance and needs user training. Evaluate adoption for device users, carers and nearby pedestrians, using both a force calculation and wider implications. Evidence limitation: These figures do not establish a safe setting for real users; qualified design testing is necessary.

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Momentum-change magnitude 40 kg m/s; average force falls from 400 N to 160 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 80 × 0.5 = 40 kg m/s. The longer stopping time changes the force, not the total required momentum change. The original average force is 40/0.1 = 400 N and the proposed force is 40/0.25 = 160 N. Both act opposite the initial motion. Relate the calculation to the specific benefit: a progressive stopping mechanism reduces average deceleration in the stated trial. 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 increases stopping distance and needs user training. Include the needs of device users, carers and nearby pedestrians, 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. These figures do not establish a safe setting for real users; qualified design testing is necessary. Report peak force, durability and relevant access constraints alongside the average-force calculation.

A low-speed mobility-device stop

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