Asked by Ashley

A small box is held in place against a rough vertical wall by someone pushing on it with a force directed upward at 28degrees above the horizontal. The coefficients of static and kinetic friction between the box and wall are 0.40 and 0.30, respectively. The box slides down unless the applied force has magnitude 18 N.

What is the mass of the box in kilograms?
Answered by BeeGray
1. Find Fn
Fn=18N*cos(28)=15.9N

2. Find Forces in Y direction to solve for m
18N*sin(28)+Fn*fs
18N*sin(28)+(15.9N*0.4)-9.8m=0

Ans: m=1.5kg
Answered by ale
where did you get the 0.4??
Answered by Wilson
That's the static coefficient of friction for the surface
Answered by Allie
2. Find Forces in Y direction to solve for m
18N*sin(28)+Fn*fs
18N*sin(28)+(15.9N*0.4)-9.8m=0

The above solution method is incorrect. I assume the intended 18N*sin(28)+(15.9N*0.4) / 9.8 = m.

The forces in the y direction divided by the acceleration would net you 1.511274299 approx mass for the object.
Answered by physics dummy
Where did the 15.9N come from?
There are no AI answers yet. The ability to request AI answers is coming soon!