Question

A horizontal force of 200N is required to cause a 15kg block to slide up an  incline with an acceleration of . Find (a) the frictional force on the block and (b) the coefficient of friction

Answer 1

Solution.

$F=200N;$

$m=15 kg;$

$\theta=20^o;$

$a=0.25 m/s;$

$ma=Fcos\theta-mgsin \theta-F_f;$

$F_f=Fcos\theta-mgsin\theta-ma;$

$F_f=200\sdot0.94-15\sdot9.8\sdot0.34-15\sdot0.25=134.27N;$

$F_f=\mu N=\mu mgcos\theta\implies \mu=\dfrac{F_f}{mgcos\theta};$

$\mu=\dfrac{134.27}{15\sdot9.8\sdot0.94}=0.97;$

Answer:$a)F_f=134.27N;$

$b)\mu=0.97.$