Question

A block weighing `4 kg` is on a plane with an incline of `(pi)/2` and friction coefficient of `4/5`. How much force, if any, is necessary to keep the block from sliding down?

Answer 1

`F>=49,05" "N`

Explanation:

`color(brown)(F_f)=color(red)(F)*mu" "mu=4/5" "color(brown)`
`color(brown)(F_f)=color(red)(F)*4/5`
`color(brown)(F_f) >=color(green)(G)`
`"Object is not slides;"`
`"if the friction force is equal or greater than weight of object"`
`4/5*F_f>=mg`
`4/5*F>=4*9,81`
`4/5*F>=39,24`
`F>=(5*39,24)/4`
`F>=49,05" "N`