Question

A wooden block is kept on a polished wooden plank whose inclination is increased gradully . The block starts slipping when the plank makes an angle of `25^(@)` with the horizontal . However , once started , the block can continue with unifrom speed , if the inclination is reduced to 21 Calculate coefficient of static and dynamic friction between the block and the plank .

Answer 1

Here angle of repose , `alpha = 25^(@)`
`:.` Coefficient of static friction ,
`mu_(s) = tan alpha = tan 25^(@) = 0.4663`
As the block continues to move uniformly , when `theta = 21^(@)` ,
`:.` Coefficient of kinetic friction , `mu_(k) = tan theta = tan 21^(@) = 0.3839 ` .