Pressing was never a big deal

A block of mass m m is pressed against a wall by a force of magnitude F F at an angle x x^{\circ} with the horizontal. Coefficient of friction between the block and wall is μ \mu .

Find the minimum force (in newton) required to keep the block at rest.

Details and assumptions :

Take g = 10 ms 2 g = 10\text{ ms}^{-2} , m = 5 kg m = \sqrt{5} \text{ kg} , μ = 0.5 \mu = 0.5 .


The answer is 20.0.

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1 solution

Rishabh Jain
Mar 8, 2016

F F is the applied force, N N is normal force, m m is the mass of block and f m f_m is the frictional force. At the end I have used the fact that maximum value of a cos θ + b sin θ a\cos \theta +b\sin \theta is a 2 + b 2 \sqrt{a^2+b^2} .

Exactly Same Way. I found the maximum using calculus, I forgot this formula, it can be proved using Cauchy-Schwarz.

Kushagra Sahni - 5 years, 3 months ago

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Right CS can be used Or simply just write it as : F = a 2 + b 2 ( sin ( θ + tan 1 a b ) ) F=\sqrt{a^2+b^2}\left(\sin \left (\theta+\tan^{-1}\frac ab\right)\right) And maximum value of sin function is 1 1 hence max of F F is a 2 + b 2 \sqrt{a^2+b^2} ...... It was a mechanics problem otherwise I would have attached the proof for the same... ;-)

Rishabh Jain - 5 years, 3 months ago

Did you saw the raw?

Department 8 - 5 years, 3 months ago

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Now I have watched it!! Did you watched how Dean Ambrose beated HHH at the end?? I really enjoyed that moment!! ;-) And Shane O' Mac is also looking energetic...

Rishabh Jain - 5 years, 3 months ago

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I will watch it all tomorrow along with SmackDown

Department 8 - 5 years, 3 months ago

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@Department 8 Right.. You'll surely enjoy the starting as well as the ending of RAW in particular ;-)

Rishabh Jain - 5 years, 3 months ago

Anyone basketball? My favorite.

Harsh Shrivastava - 5 years, 3 months ago

Anyone of you watches cricket? I simply love cricket and watch every match irrespective of the country.

Kushagra Sahni - 5 years, 3 months ago

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Same here.. I'm also a die hard fan of cricket.... I also appreciate beauty of cricket but I cannot love any another team other than India not because its my country but because they play beautifully.. But anyways my favourite cricketer is AB Devillers.. ;-)

Rishabh Jain - 5 years, 3 months ago

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@Rishabh Jain My favourite team is surprisingly Australia just because the way they play. I loved Mike Hussey, now I like Warner, DeVilliers, Steve Smith, Adam Voges, Virat Kohli and everyone else who succeeds in entertaining me.

Kushagra Sahni - 5 years, 3 months ago

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@Kushagra Sahni Cricket is something more like a game I always hated because of my friends who would always cheated to win the match.

Department 8 - 5 years, 3 months ago

@Kushagra Sahni Ya... Australia was \textbf{was} a dominating team.. I loved it when it had players like Lee, Warne ,Pointing, McGrath , Gilchrist, Hayden, and many more .. But now the focus is shifted to team India which is producing new young talents each day...

Rishabh Jain - 5 years, 3 months ago

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