Statics Problem Tipping Refrigerator

[spacetimedude]

Homework Statement

A refrigerator with a mass of 100kg measures 150cm high by 75 cm wide by 75 cm deep. How much force applied horizontally at the top edge of the front will make it start tipping backward? Assume that the center of mass is at the center of the refrigerator.

Homework Equations

Moment= r x F

The Attempt at a Solution

I do not know how to start this problem. I have drawn a 3D figure of the refrigerator and have ∑Fy=mg+N (vector) and ∑Fx=F+Ff (force applied+force of friction, again vector). All the previous examples I was given were the typical ladder leaning on the wall type of questions but this one has three dimensions.

Any tips will be appreciated.

 

[PhanthomJay]

Homework Statement

A refrigerator with a mass of 100kg measures 150cm high by 75 cm wide by 75 cm deep. How much force applied horizontally at the top edge of the front will make it start tipping backward? Assume that the center of mass is at the center of the refrigerator.

Homework Equations

Moment= r x F

The Attempt at a Solution

I do not know how to start this problem. I have drawn a 3D figure of the refrigerator and have ∑Fy=mg+N (vector) and ∑Fx=F+Ff (force applied+force of friction, again vector). All the previous examples I was given were the typical ladder leaning on the wall type of questions but this one has three dimensions.

Any tips will be appreciated.

You can look at this in 2D. A rectangle 150 cm tall and 75 cm wide with a force applied horizontally at the top. Note that for tipping to occur, the normal force must all be located where?

 

[spacetimedude]

Is the normal force located at the bottom edge of the rectangle since when it is tipping, it is focused on one place?

 

[PhanthomJay]

Is the normal force located at the bottom edge of the rectangle since when it is tipping, it is focused on one place?

Focused in one place yes but where along the bottom edge?

 

[spacetimedude]

I was just thinking as a rectangle so on the vertex, but do we have to consider the depth in 3D as well?

 

[haruspex]

I was just thinking as a rectangle so on the vertex, but do we have to consider the depth in 3D as well?

To be pedantic, it says the force is applied at the front top edge. Your FBD should be a side view, so the depth matters but the width doesn't. However, since depth and width are equal here it's the same either way.

 

[SammyS]

Gosh! I wanted to see the 3D figure, but then it occurred to me,"I only have a 2D monitor."