Question

1. A loaded sled weighing 85 N rests on an inclined plane at an angle of 15 o to

the horizontal as in the figure below. The coefficient of static friction between

the sled and the inclined plane is 0.25. Calculate the minimum force, F

parallel to the inclined plane, that will prevent the sled from slipping down.

Answer 1

Solution.

$F_g=85N;$

$\mu=0.25;$

$F_f=\mu N;$

$N=F_gcos\alpha;$

$F_f+F-F_gsin\alpha=0;\implies F=F_gsin\alpha-F_f=F_gsin\alpha-\mu F_gcos\alpha;$

$F=85\sdot0.2588-0.25\sdot85\sdot0.9659=1.473N;$

Answer:$F=1.473N.$