An object of mass 3 kg rests on a horizontal plane and is pulled along the plane by a force of 15 N at an angle of 30º to the plane. The acceleration due to gravity is 9.8 m/s2. If this force is just sufficient to start motion, the coefficient of static friction is:
A) 0.09
B) 0.44
C) 0.57
D) 0.59

Question

Quizplus · Accepted Answer

The force of friction is equal to the force applied multiplied by the coefficient of static friction. The force of friction is also equal to the mass of the object multiplied by the acceleration due to gravity multiplied by the sine of the angle of the force. Setting these two equations equal to each other and solving for the coefficient of static friction gives:$$μ_s = \frac{F}{mg\sinθ} = \frac{15 N}{(3 kg)(9.8 m/s^2)\sin30°} = 0.59$$

An Object of Mass 3 Kg Rests on a Horizontal