Question 158: Centre of Mass and Rotational Motion

Question

A $$\sqrt {34} $$ m long ladder weighing 10 kg leans on a frictionless wall. Its feet rest on the floor 3 m away from the wall as shown in the figure. If Ef and Fw are the reaction forces of the floor and the wall, then ratio of $${F_w}/{F_f}$$ will be :
(Use g = 10 m/s2.)

Accepted Answer

Taking torque from B
$${F_w} 	imes 5 = {3 \over 2}mg$$
$$ \Rightarrow {F_w} = {3 \over {10}} 	imes 10 	imes 10$$
$$ = 30\,N$$
$$N = mg = 100\,N$$
and $${f_r} = {F_w} = 30\,N$$
so $${F_f} = \sqrt {{N^2} + f_r^2}  = \sqrt {10900}  = 10\sqrt {109} \,N$$
so $${{{F_w}} \over {{F_f}}} = {3 \over {\sqrt {109} }}$$

Answer

$${6 \over {\sqrt {110} }}$$

Answer

$${3 \over {\sqrt {113} }}$$

Answer

$${3 \over {\sqrt {109} }}$$

Answer

$${2 \over {\sqrt {109} }}$$

Centre of Mass and Rotational Motion

A $\sqrt {34} m long ladder weighing 10 kg leans on a frictionless wall. Its feet rest on the floor 3 m away from the wall as shown in the figure. If Ef and Fw are the reaction forces of the floor and the wall, then ratio of {F_w}/{F_f}$ will be : (Use g = 10 m/s2.)

Choose the correct answer: