A 4.4kg block is pushed along the ceiling

[madelines]

Homework Statement

A 4.40 kg block is pushed along the ceiling with an constant applied force of F = 84.0 N that acts at an angle θ = 50° with the horizontal. The block accelerates to the right at 6.92 m/s2. Determine the coefficient of kinetic friction between the block and the ceiling.

Homework Equations

u_k=(F_k)/(F_n)
ƩF=m*a
(pythagorean theorem for F_n)

The Attempt at a Solution

I've tried this problem multiple different ways, but I keep getting a number that is greater than 1. Thank you!

F_n=(4.4*9.8)-(84*sin50)=-21.227733
-F_k=(4.4*6.92)-(84*cos50)=-23.546259
u_k=1.1092
but 0<u_k<1

 

[CWatters]

I haven't checked your working but..

http://en.wikipedia.org/wiki/Friction#Coefficient_of_friction

Occasionally it is maintained that µ is always < 1, but this is not true. While in most relevant applications µ < 1, a value above 1 merely implies that the force required to slide an object along the surface is greater than the normal force of the surface on the object. For example, silicone rubber or acrylic rubber-coated surfaces have a coefficient of friction that can be substantially larger than 1.

 

[madelines]

Thank you! That cleared up some of the confusion!