Physics

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A dock worker loading crates on a ship
finds that a 18 kg crate, initially at rest on a horizontal surface, requires a 71 N horizontal force to set it in motion. However, after the crate is in motion, a horizontal force of 46 N is required to keep it moving with a constant speed. The acceleration of gravity is 9.8 m/s
2.
Find the coefficient of static friction between crate and floor.

  • Physics -

    Answering my own question here, but...
    µs (static friction)
    Ffs (peak frictional force)
    Fn (Normal force -needs to be in Newtons-)
    Ffs = µs * Fn
    71 = µs * (18 * 9.8)
    71 = µs * 176.4
    71 / 176.4 = µs * 176.4 / 176.4 (isolates the variable µs)
    .4024943311 = µs

    replaces 71 with 46 to find µk ( kinetic friction)

  • Physics -

    Answering my own question here, but...
    µs (static friction)
    Ffs (peak frictional force)
    Fn (Normal force -needs to be in Newtons-)
    Ffs = µs * Fn
    71 = µs * (18 * 9.8)
    71 = µs * 176.4
    71 / 176.4 = µs * 176.4 / 176.4 (isolates the variable µs)
    .4024943311 = µs

    replace 71 with 46 to find µk ( kinetic friction)

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