A dockworker loading crates on a ship finds that a 25-kg crate, initially at rest on a horizontal surface, requires a 72-N horizontal force to set it in motion. However, after the crate is in motion, a horizontal force of 55 N is required to keep it moving with a constant speed. Find the coefficients of static and kinetic friction between crate and floor.

Question

Jean Collier

Physics

7 June, 23:57

A dockworker loading crates on a ship finds that a 25-kg crate, initially at rest on a horizontal surface, requires a 72-N horizontal force to set it in motion. However, after the crate is in motion, a horizontal force of 55 N is required to keep it moving with a constant speed. Find the coefficients of static and kinetic friction between crate and floor.

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Answers (1)

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Ean Vaughan · Answer 1

Force of static friction = μs x mg

Given force of static friction = 72 N

μs x mg = 72

μs = 72 / mg

= 72 / 25 x 9.8

=.294

Force of kinetic friction = μk x mg

Given force of kinetic friction = 55

μk x mg = 55

μk = 55 / mg

= 55 / 25 x 9.8

=.2245