Question

16. A 15.0 kg box rests on a flat table. The coefficient of kinetic friction between the table and the box is 0.20, and the coefficient of static friction is 0.25. A string pulls on the box with a force of 78 N at 0.0o. Using appropriate quantitative problem-solving steps, determine whether the box remains at rest or accelerates. If the box accelerates, determine the acceleration.

A) Calculate the maximum static friction. Keep four sf.

B) Calculate the kinetic friction. Keep three sf.

C) As the box slides, what is the net force acting on the box? Keep three sf.

D) What is the acceleration of the box? Keep two sf.

(SF means significant figures)

Answer 1

Given the mass of the box m = 15kg, the coefficient of kinetic friction between the table and the box is = 0.20, the coefficient of static friction between the table and the box is = 0.25 and the appliet force F = 78N.

A) The maximum value of static friction (fmax) is given by,

Here fmax is less than the applied force F. So the box accelerates.

B) The kinetic friction is given by,

C) When the body slides, the net force (Fnet) is given by,

D) The acceleration of the box (a) is given by,