Normal Force and Coefficient of kinetic friction (Quiz 4, q15)

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Homework Help Overview

The problem involves analyzing the forces acting on a box being pushed up an inclined plane, specifically focusing on the normal force and the coefficient of kinetic friction. The context includes a horizontal force applied to the box and the effects of gravity and the incline angle.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculation of the normal force, with initial attempts focusing on the weight of the box. Questions arise regarding the influence of the incline angle and the need to account for additional forces acting on the box.

Discussion Status

Some participants have provided guidance on considering the angle of the incline and suggested listing forces in different directions to formulate equations. There is an ongoing exploration of the correct approach to determine the normal force and friction coefficient.

Contextual Notes

Participants note that the angle of the incline has not been adequately incorporated into the calculations, and there is a suggestion to analyze forces in both vertical and horizontal directions or along the plane and normal to the plane.

gcombina
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A 250-N force is directed horizontally as shown to push a 29-kg box up an inclined plane at a constant speed. Determine the magnitude of the normal force, FN, and the coefficient of kinetic friction, µk.
FN µk
(a) 330 N 0.31
(b) 310 N 0.33
(c) 250 N 0.27
(d) 290 N 0.30
(e) 370 N 0.26

My attempt:

I know FN = mg
so FN = (29kg) (9.8 m/s^2)
FN = 284

why is it not right?
 

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From the diagram and equations you've provided, it doesn't appear that you've accounted for the angle of the incline. Try to account for that.
 
ok FN = Mg
= 250N sin 27
= 113

still not the right answer
 
squelch said:
From the diagram and equations you've provided, it doesn't appear that you've accounted for the angle of the incline. Try to account for that.
That's not the only omission.
gcombina, choose two directions, e.g. vertical and horizontal. In each direction, list all the forces that act in that direction. What two equations can you write?
(if you prefer, you can choose parallel to the plane and normal to the plane, or horizontal and normal to the plane, whatever.)
 

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