A boy (30 kg) sitting on his horse whips it. the horse speeds up at an average adcceleration of `2.0 m/s^2`. (A). If the boy does not slide back, what is the force of friction exerted by the horse on the boy? (b).If the boy slides back during the acceleration, what can be said about the coefficient of static friction between the horse and the boy.
`Take = 10 m/s^2`

Explanation

(a) As the boy does not slide back , its acceleration = acc of the horce
`:. f_(s) = M a = 30 (2.0) = 60 N`
(b) If the boy slides back the horse could not nexert a friction of `60` N on the boy
Maximum force of static friction `f_(s) = mu_(s) R= mu_(s) (M g) :. mu_(s) (30) (10) le 60 N`
`:.` Max value of coeff of static friction `= mu_(s) = (60)/(300) = 0.20` .