Answer:
The coefficient of static friction is
![\mu= 0.7667](https://img.qammunity.org/2021/formulas/physics/college/c1xlk92efmu8delonitphybmu6i4ssubiw.png)
Step-by-step explanation:
From the question we are told that
The acceleration is
![a = 6.9 m/s^2](https://img.qammunity.org/2021/formulas/physics/college/nzt84nce8z6mvh7sc0lsu6lovfo6nc076v.png)
The mathematical expression that show the relationship between frictional force and the sliding force of the cabinet at the point just before sliding begins is
![F_f = F_s](https://img.qammunity.org/2021/formulas/physics/college/zop8fbqcxuftfrjny6d1cwcyhmgcn49af2.png)
Now
![F_f = mg\mu](https://img.qammunity.org/2021/formulas/physics/college/7mxga05z4hpp4axszkamevf8kome1h1uyk.png)
Where m is the mass of the cabinet
g is the acceleration due to gravity
is the coefficient of static friction
And
Where a is the acceleration due to gravity
Now substituting this into the equation
![mg \mu = ma](https://img.qammunity.org/2021/formulas/physics/college/566xquuj2wd6v96zjzbddz93y8h0jdxnqr.png)
![g\mu =a](https://img.qammunity.org/2021/formulas/physics/college/aane6p46jn77gn5wtocdw9jz3ddbpgu96j.png)
![\mu = (a)/(g)](https://img.qammunity.org/2021/formulas/physics/college/k07l3xk6sl7lo2nfvt2ebb0xmvbk6v53oh.png)
Substituting values where
![g =9.8m/s^2](https://img.qammunity.org/2021/formulas/physics/middle-school/rdasm34tml8aj0uyn7gvcdpkhoicf6du4u.png)
![\mu = (6.9)/(9.8)](https://img.qammunity.org/2021/formulas/physics/college/fbjmkdixij0uibi15r03nvusdbh3opa0sd.png)