A uniform rod of mass M and
length L is resting between a
rough wall and a rough floor as
shown in the figure. The
coefficient of friction between any
two surface is
. For angle
for
which the rod is just on the verge
of slipping is
.
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Photo to know the direction of reactions..
First start with conditions of stability ∑ F x = ∑ F y = ∑ M = 0 Let's assume that reaction at end point is the rod in vertical surface is R 1 and has distance X from horizontal surface , friction force equal to R 1 × μ we will also named it as F . And the reaction at end point of the rod at horizontal surface is R 2 and has distance S from the vertical surface , friction force equal to R 2 × μ . N o t e that t a n θ = S X
So we get from equations of equilibrium R 1 = R 2 × μ ( 1 ) R 2 + R 1 × μ = M from ( 1 ) we get R 2 = 1 + μ 2 M ( 2 ) Now we will take the Moment around point F we get R 2 × μ × X + M × 2 S = R 2 × S using ( 2 ) we have 1 + μ 2 M ∗ X ∗ μ + 2 M ∗ S = 1 + μ 2 M ∗ S Then dividing by S we get S X ∗ 1 + μ 2 μ = 1 + μ 2 1 − 2 1 Then S X = μ 1 − 2 μ 1 + μ 2 = 2 μ 1 − μ 2