Sriram MB volunteered to help out in a Physics 2A demonstrat

Sriram MB volunteered to help out in a Physics 2A demonstration by sitting on a stool that easily rotates. As Sriram holds the dumbbells with his anus extended. Professor temporarily applies a sufficient torque that causes him to rotate fairly rapidly. Then, Sriram pulls in his arms, bringing the dumbbells close to his body. When Sriram pulls in his arms: his angular velocity decreases. his rotational kinetic energy decreases. his rotational inertia increases. his angular momentum remains the same. his angular velocity remains the same. 24. A 6.0-m-long. uniform ladder of mass 94.0 kg rests against a friction\'s wall. The coefficient of static friction between the ladder and the ground is 1.2. and the ladder makes a 30.0\" angle with the ground. What is the mass of the heaviest person who can ascend to the top of the ladder before the ladder begins to slip? I

Solution

23. when dumbell are pulled that happens due to internal force
man-dumbell system.

hence angular momentum will be conserved.

Ii wi = If wf

when dumbells are pulled closed to body then moment of inertia
of system decreases.

hence angular speed increases.

Ans(d)

24.

consider, man of mass m is at the top.

then balancing moment about floor point,

(6/2 * 94 g cos30) + (6 * mg cos30) - (6 * Nw * sin30) = 0

Nw is the normal force due to wall in horizontal direction,.

244.2g + 5.2mg - 3Nw = 0

and balancing forces in vertical,

Nf - mg - 94g = 0

Nf = (94 + m)g

and friction force, f = us Nf = 1.2(94 + m)g

and in horizontal, f - Nw = 0

Nw = f

244.2g + 5.2mg - 3Nw = 0 (putting Nw )

244.2g + 5.2mg - 3*1.2(94 + m)g = 0

-94.2g + 1.6mg =0

m = 94.2/1.6 = 58.9 kg

Ans(B)