Question

An object with a mass of `9 kg` is on a plane with an incline of `- pi/4`. If it takes `24 N` to start pushing the object down the plane and `9 N` to keep pushing it, what are the coefficients of static and kinetic friction?

Answer 1

Static friction coefficient=1.4

Kinetic friction coefficient=0.144

Explanation:

m=9kg;`theta`=45°;g=`9.8ms^-1`
In 1st case,
`mu`mg`costheta`=24+mg`sintheta`
`=>(mu-1)/sqrt2=(24×sqrt2)/(9×9.8)`
`=>mu=1.4`
In 2nd case,
`mu`mg`costheta`=9
`=>mu=(9×sqrt2)/(9×9.8)`
`=>mu=0.144`