Finding Friction Force & Work with No Applied Force

[kara123]

Homework Statement

How much work is done by pushing a 15 kg box at a constant velocity across a horizontal floor with a coefficient of friction of 0.68 for a distance of 8.0 m?

Relevant Equations

Ff=coefficent of friction x FN
FN=mg
W=fxd

-i had begun by finding the normal force =147 N
-then found the force of friction=99.96 N
-found the work of friction=-799.68 J
after that I am unsure of where to go since I don't have a force applied

 

[PeroK]

What can you say about the applied force?

Hint: you are told velocity is constant.

 

[kara123]

would it be zero since acceleration is zero

 

[PeroK]

would it be zero since acceleration is zero

Acceleration is zero, but there's friction to overcome!

 

[kara123]

so since work of friction equals -799.68 J then work applied must equal 799.68 J or excel it?

 

[PeroK]

so since work of friction equals -799.68 J then work applied must equal 799.68 J or excel it?

It can't exceed it, as then the box would have gained KE.

 

[kara123]

okay so the answer would be 799.68 J of work is done by pushing a 15kg box across a horizontal floor at a constant velocity

 

[PeroK]

Yes, except you don't have data to five decimal places.

 

[kara123]

got it thank you!