A uniform disk, a thin hoop, and a uniform sphere, all with the same mass and sa

Question

A uniform disk, a thin hoop, and a uniform sphere, all with the same mass and same outer radius, are each free to rotate about a fixed axis through its center. Assume the hoop is connected to the rotation axis by light spokes. With the objects starting from rest, identical forces are simultaneously applied to the rims, as shown. Rank the objects according to their angular momenta after a given time I. least to greatest. all tie disk. hoop, sphere hoop. disk, sphere hoop, sphere, disk A playground merry-go-round has a radius of 3.0 m and a rotational inertia of 600 kg' m. It is initially spinning at 0.80 rad/s when a 20-kg child crawls from the center to the rim. When the child reaches the rim the angular velocity of the merry -go-round is: 0.62 rad/s 0.73 rad/s 0.80 rad/s 0.89 rad/s 1.1 rad/s The angular momentum vector of Earth, due to its daily rotation, is directed: tangent to the equator toward the cast tangent to the equator toward the west north south toward the sun A 160-N child sits on a light swing and is pulled back and held with a horizontal force of 100 N. The magnitude of the tension force of each of the two supporting ropes is: 60 N 94 N 120 N 190N 260 N

Explanation / Answer

33 ans

the angular momentum L=Iw

so disk momentum of inertia I=0.5Io

the momentum of inertia of the hoop=Io

the momentum of inertia of the sphere=0.4Io

the angular momentum is basing on momentum of inertia of given bodys

so the rank order is hoop,disk,sphere

so the correct option is C

34 ans

radius r=3 m

momentum of inertia I1=600 kg.m^2

angular velocity W1=0.80 rad/s

mass m=20 kg

basing on the principle of law of conservation of momentum

I1W1=(mr^2)W2

600*0.80=(20*3^2)W2

480=180*W2

W2=2.67 rad/s

35 ans

the angular momentum of the vector is depends upon to wards the sun

because the momentum of inertia of sun is very high

the correct option is E

36 ans

force F1=160 N

force F2=100 N

therefore the tension in the string T=F1-F2=160-100=60 N

the correct option is A

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