= Constant-speed measurement of kinetic friction
{title2=$\mu_k=\overline F/(mg)$}
A force gauge reads the pulling <force>. For horizontal straight-line sliding at constant <velocity>, its reading equals the opposing <kinetic friction> magnitude, provided these are the only horizontal <forces>. For total supported <mass> $m$, including added loads, $N=mg$, so a mean sliding reading $\overline F$ gives $\mu_k=\overline F/(mg)$. The important readout is the sustained sliding force after the starting peak; the peak belongs to the <static friction> threshold.
The University of Mississippi's Experiment 6 uses a wooden block on a wooden plane, a triple-beam balance, added masses, and a dual-range 50 N force probe connected through LabPro to Logger Pro. Its procedure calibrates the probe with a $0.5\,\mathrm{kg}$ load on a hanger, entering the corresponding <force> in newtons, and measures the block's <mass> separately. With the plane horizontal, it starts with $0.5\,\mathrm{kg}$ on the block and pulls horizontally at constant <speed>. The recorded <force> trace has a starting peak; the procedure selects the subsequent constant-force interval and takes its <mean>. It repeats with $0.5\,\mathrm{kg}$ increments up to $3\,\mathrm{kg}$ added, then plots sliding <force> against <normal force> to estimate the <coefficient of kinetic friction> from the <slope>.<Experiment 6: The Coefficient of Friction (University of Mississippi teaching laboratory)>[Experiment 6, The Coefficient of Friction, PDF pp. 1–2: Equipment, Objectives, Procedure steps 1–7]{ref}
For a replication, check the gauge's zero with the string slack and its response to known <gravitational weights>; zeroing alone does not check its scale. Keep the plane level, the pull parallel to it, and the block face and track region consistent. Specify the contacting materials and whether the surfaces are dry, cleaned or lubricated; repeat runs to see whether debris or wear changes the sliding <force>. Verify constant <velocity> independently from <position> versus <time>, rather than assuming that a flat force trace proves zero <acceleration>. These are proposed measurement controls, not additional observations from the laboratory writeup. Record the selected interval, variation between runs and gauge resolution as sources of <measurement error>.
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