A 3 4 m long ladder weighing 10kg leans on a frictionless wall. Its feet rest on the floor 3m away from the wall as shown in the figure. If Ff and Fw are the reaction forces of the floor and the wall, then ratio of Fw / Ff will be:

(Use g = 10 m/s2)

 

Option 1 - <p><span class="mathml" contenteditable="false"> <math> <mrow> <mfrac> <mrow> <mn>6</mn> </mrow> <mrow> <mroot> <mrow> <mn>1</mn> <mn>1</mn> <mn>0</mn> </mrow> <mrow></mrow> </mroot> </mrow> </mfrac> </mrow> </math> </span></p>
Option 2 - <p><span class="mathml" contenteditable="false"> <math> <mrow> <mfrac> <mrow> <mn>3</mn> </mrow> <mrow> <mroot> <mrow> <mn>1</mn> <mn>1</mn> <mn>3</mn> </mrow> <mrow></mrow> </mroot> </mrow> </mfrac> </mrow> </math> </span></p>
Option 3 - <p><span class="mathml" contenteditable="false"> <math> <mrow> <mfrac> <mrow> <mn>3</mn> </mrow> <mrow> <mroot> <mrow> <mn>1</mn> <mn>0</mn> <mn>9</mn> </mrow> <mrow></mrow> </mroot> </mrow> </mfrac> </mrow> </math> </span></p>
Option 4 - <p><span class="mathml" contenteditable="false"> <math> <mrow> <mfrac> <mrow> <mn>2</mn> </mrow> <mrow> <mroot> <mrow> <mn>1</mn> <mn>0</mn> <mn>9</mn> </mrow> <mrow></mrow> </mroot> </mrow> </mfrac> </mrow> </math> </span></p>
10 Views|Posted 6 months ago
Asked by Shiksha User
1 Answer
A
6 months ago
Correct Option - 3
Detailed Solution:

mg = 10 * 10

= 100 of

NA = Fω reaction force offered by the wall

N32+fB2=Ff reaction force offered by the floor.

By NLM 1

Translational fB = NA

NB = mg = 100N

Ac2 + Bc2 = AB2

Ac2 = 34 – 9

Ac = 5m

Rotational equilibrium τB=0

mg l2cosθ=NAlsinθ

100cosθ2=NAsinθ

NA = 50 cot

Now cot = 35

NA 50*35=30N

Therefore, NA = Fω=30N - (i)

Ff=NB2+fB2=1002+302=10109N - (2)

fωFf=3010109=3109

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