A 25 kg chair initally at rest on a horizontal floor requires a 165 N horizontal force to set it in motion. Once the chair is in motion, a 127 N horizontal force keeps it moving at a constant velocity. (a) Find the coefficient of static friction between the chair and the floor. (b) Find the coefficient of kinetic friction between the chair and the floor.
2007-12-18 03:43:13 · 2 answers · asked by Anonymous in Science & Mathematics ➔ Physics
The coefficient of static friction = (maximum force applied to first move object) / (normal force) or in mathematical terms,
us = Fsmax / Fn
Calculate normal force by finding the gravitational force.
Fg = ma = (25 kg) * (9.8 m/s^2) = 245N
Fn must equal the force due to gravity, so Fn = 245N
us = 165/245 = 0.673
The coefficient of kinetic friction = (force needed to keep object moving at constant speed) / (normal force) or in mathematical terms,
uk = F / Fn
uk = 127/245 = 0.518
2007-12-18 04:10:31 · answer #1 · answered by Katy D 4 · 0⤊ 0⤋
25*9.81*µs=165
µs=0.67
25*9.81*µk=127
µk=0.518
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2007-12-18 11:51:02 · answer #2 · answered by odu83 7 · 0⤊ 0⤋