A rock-climber (49 kg) is managing to be at rest between two vertical rocks pressing one rock A by his feet and the other B by his back . If the coefficient of friction between his shoes and wall is A `1.2` while between his back and wall B is `0.8` and limiting friction acts at all the contacts , then : (a) What is his push against the rock ? (b) What percent of the weight is supported by the frictional force an legs ?

Answer

(a) 240 N , (b) `60%`

Explanation

(a) as `" " N_(A) = N_(B)`
Now `" " mu_(A)N_(A) + mu_(B) N_(B) = Mg`
`N_(A)[ mu_(A) + mu_(B) ] = Mg`
`N_(A) = (Mg)/(mu_(A) + mu_(B))`
(b) `" " f_(A) = mu_(A) N_(A)`
Now present of weight supported by it is
`= (mu_(A) N_(A))/(Mg) xx 100`