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Grade 12Mechanics

A uniform cube of mass m & side a is rsting on a rough 45 degree inclined surface. The distance of the point of application of normal reaction measured from the lower edge of the cube is:

a) zero

b) a/3

c) a/√2

d) a/4

Profile image of neeraj pawar
16 Years agoGrade 12
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3 Answers

Profile image of anandpal shekhawat
16 Years ago

hi,

as normal rxn passes through centre & perpendicular to lower & upper faces & gap between centre & lower edge is

a/21/2

so (c) is correct. 


Profile image of neeraj pawar
16 Years ago

no!!! ans is (a)

Profile image of anandpal shekhawat
16 Years ago

hi, 

sorry for wrong ans.

now we will approach it as a case of toppling

MgsinΘ  is the component of weight which acts on centre at a distance a/2 from lower edge. so its torque will be

Τ1= MgsinΘ*a/2(.)

& normal  will nullify this effect so

T2 = MgcosΘ*r(×)

equating both

r=a/2 (from centre)

as normal passes through lower face

hence normal will pass through edge.

 

 

 

 

regards

anand