A uniform rectangular block ( dimentions are LxWxH, with W<L<H) of mass M rests
ID: 2131207 • Letter: A
Question
A uniform rectangular block ( dimentions are LxWxH, with W<L<H) of mass M rests on the floor with coefficient of static friction mu (u). You want to apply a force F horizontally on the block to push it across the floor. How high above the floor must you apply the force to make the block slide and not tip over? Put you answer in terms of the mass and dimensions. Assume the block is standing with its smallest face in contact with the floor, and you push on the largest face.
Explanation / Answer
writing the equation of forces acting on the block, we have
N=mg
uN=F
so F=umg
also let F is applieed at a height h above the floor
and mg is acting vertically downwards at a distance W/2 from the edge about which it may topple
then taking the torque of the forces about that edge, we have
Fh=mgW/2
=>h=mgW/2F
=>h=mgW/2umg
=>h=W/2u
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