Question

30 kg 125 N

What is the minimum downward force on the box in the figure that will keep it from slipping?(Figure 1) The coefficients of static and kinetic friction between the box and the floor are 0.34 and 0.24, respectively.

Express your answer to two significant figures and include the appropriate units.

F= ___ N

Answer 1

From the given question,

Weight of the box(W) = 30kg= 300N

Normal reaction(R)=300+F

Horizontal driving force=125N

Since the box is at rest.we will use coefficient of static friction. $\mu _{s}$ = 0.34

Frictional force= $\mu _{s}$ R= (0.34)(300+F)

for limiting case

Frictional force = driving force

(0.34)(300+F) = 125

F= 67.64N

or F= 68N