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all surfaces are frictionless. three cylinders are placed as shown in the diagram. find the least angle θ that prevents the arrangement from collapsing
1. tan-11/2
2.tan-11/2√3
3.tan-11/3√3
4.tan-11/4√3

this is for 2010 aspirants..seniors plz dont post solution now.

16 Answers

62
Lokesh Verma ·

awesome question..

no takers?

11
virang1 Jhaveri ·

Is it ∩/4?

1
Samarth Kashyap ·

sorry virang, i've given the options. anyway, post ur method, maybe ur method is right and have made mistake in calculations.

11
virang1 Jhaveri ·

Mg is the downward force of the top cylinder pushing it downwards
This force pushes the two cylinder upwards
Therefore
Mg = √(2p2+2p2cos180-2θ)
The force which keeps the cylinder stable is mgsinθ
p - mgsinθ = 0
mg/√(2-2cos2θ) - mgsinθ = 0
1/√2*2sin2θ = sinθ
1/2 = sin2θ
Sin θ = 1/√2
θ = 45°

3
msp ·

2

11
virang1 Jhaveri ·

IS my method rite?

1
Samarth Kashyap ·

i think u have made mistake in ur fbd itself.

1
Samarth Kashyap ·

W=2N1cos 30
therefore N1=W/√3

1
Samarth Kashyap ·

N2sinθ=N1sin 30..............(2)
N2cosθ=N1cosθ + W.........(3)

when they are just not collapsing the two cylinders at the bottom dont exert any forces on each other.

dividing (2) and (3) we get tanθ=1/3√3
or θ=tan-11/3√3

62
Lokesh Verma ·

Good work :)

1
Samarth Kashyap ·

if the coefficient of friction is μ, find the normal reaction N1 and N2 offered by surfaces A and B on the cylinder.
the cylinder is not in equilibrium

106
Asish Mahapatra ·

is w const. or is it initial w?

1
Samarth Kashyap ·

ω is the initial value... u have to find out the normal reaction at the initial instant of time..

106
Asish Mahapatra ·

N1cosθ+N2cosθ+μN1sinθ-μN2sinθ = W ... (i)
N1sinθ = N2sinθ+μN1cosθ+μN2cosθ ... (ii)

1
Samarth Kashyap ·

sorry for wasting ur preious time, forgot to mention that the cylinder is not in equilibrium....

i mean to say, it tends to roll....

i'm not sure whether the situation is possible, but the ans i got is
N1= mg(1+μ)
.....................
2sinθ(1+μ2)

N2= mgμ
...................
2sinθ(1+μ2)

pls forgive me if my ques is wrong.

106
Asish Mahapatra ·

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