Physics, 11.03.2020 19:44 cardenas08

A 60.0-kg crate rests on a level floor at a shipping dock. The coefficients of static and kinetic friction are 0.760 and 0.410, respectively. What horizontal pushing force is required to (a) just start the crate moving and (b) slide the crate across the dock at constant speed

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Answer from: LizaB15

The horizontal pushing force required to just start the crate moving is 447 N.The horizontal pushing force required to slide the crate across the dock at a constant speed is 241 N.

Explanation:

By the definition of the coefficient of static friction we have:

μ $_{s}$ = $\frac{F_{appl} }{W}= \frac{F_{s} }{N}$ ,

where, $F_{appl}$ is the horizontal pushing force,

W = mg is the weight of the crate directed downward,

$F_{s}$ is the static friction force-directed opposite to the horizontal pushing force and equal to it,

N is the force of reaction directed upward and equal to the weight of the crate.

From this formula we can find the horizontal pushing force required to just start the crate moving:

$F_{appl} = F_{s} = u_{s}N = u_{s}mg$

= 0.760 $\times$ 60 kg $\times$ 9.8 m / s^2

= 447 N.

By the definition of the coefficient of kinetic friction we have:

u $_{k} = \frac{F_{appl} }{W} = \frac{F_{k} }{N}$ ,

where, $F_{appl}$ is the horizontal pushing force,

W = mg is the weight of the crate directed downward,

$F_{k}$ is the kinetic friction force-directed opposite to the horizontal pushing force and equal to it,

N is the force of reaction directed upward and equal to the weight of the crate.

From this formula we can find the horizontal pushing force required to slide the crate across the dock at a constant speed:

$F_{appl} = F_{k} = u_{k}N = u_{k}mg$

= 0.410 $\times$ 60 $\times$ 9.8

= 241 N.

The horizontal pushing force required to just start the crate moving is 447 N.The horizontal pushing force required to slide the crate across the dock at a constant speed is 241 N.

Answer from: Quest

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this. hope that you like the video and that it explains more in detail to you.

that is the link.

Answer from: Quest

i just did an experiment like this in my science class. also the answer is yes, it will get separated because they are two opposites meaning if they are opposite they can not attract.

hope this .!

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A 60.0-kg crate rests on a level floor at a shipping dock. The coefficients of static and kinetic fr...