Problem 512 | Friction

Problem 512
A homogeneous block of weight W rests upon the incline shown in Fig. P-512. If the coefficient of friction is 0.30, determine the greatest height h at which a force P parallel to the incline may be applied so that the block will slide up the incline without tipping over.
 

Tall block on an inclined plane

 

Solution 512

 
MONGOL○482

Good day sir! Why is the normal force not considered when we summate moments about A? Is it because the normal force equals the vertical component of the weight with respect to the inclined plane? If so, why dont we just cancel the two(Wy & N) so that whats left is Ph=Wx(40cm)? Please help sir.

Jhun Vert
Jhun Vert's picture

why dont we just cancel the two(Wy & N) so that whats left is Ph=Wx(40cm)?

In tipping over, the mode of impending motion is rotation; about A in this problem. When the block is about to tip over, there will be no N but the component of weight in the y-direction is still there.

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