A 60.1-kg crate rests on a level floor at a shipping dock. The coefficients of static...

A 60.1-kg crate rests on a level floor at a shipping dock. The coefficients of static and kinetic friction are 0.515 and 0.406, respectively. What horizontal pushing force is required to (a) just start the crate moving and (b) slide the crate across the dock at a constant speed?

Solutions

Expert Solution

Gravitational acceleration = g = 9.81 m/s²

Mass of the crate = m = 60.1 kg

Normal force on the crate from the level floor = N

N = mg

To start moving the crate the force needed is equal to the force of the static friction.

Coefficient of static friction = _s = 0.515

Maximum static friction force on the crate = f_s

f_s = _sN

f_s = _smg

f_s = (0.515)(60.1)(9.81)

f_s = 303.6 N

To push the crate at a constant speed across the crate the force needed is equal to the force of the kinetic friction.

Coefficient of kinetic friction = _k = 0.406

Maximum kinetic friction force on the crate = f_k

f_k = _kN

f_k = _kmg

f_k = (0.406)(60.1)(9.81)

f_k = 239.4 N

a) Horizontal pushing force required to just start moving the crate = 303.6 N

b) Horizontal pushing force required to slide the crate at a constant speed across the dock = 239.4 N

genius_generous answered 4 months ago

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