45 to 47 A photograph record is dropped onto a freely spinning turntable. Then:

Question

45 to 47

A photograph record is dropped onto a freely spinning turntable. Then: A) neither angular momentum nor mechanical energy is conserved because of the frictional forces between record and turntable. B) the frictional force between record and turntable increases the total angular momentum C) the frictional force between record and turntable decreases the total angular momentum D) the total angular momentum remains constant E) the sum of the angular momentum and rotational kinetic energy remains constant Block A, with a mass of 4 kg, is moving with a speed of 2.0 m/s while block B, with a mass of 8 kg, is moving in the opposite direction with a speed of 3 m/s. The center of mass of the two block-system is moving with the velocity of: A) 1.3 m/s in the same direction as A B) 1.3 m/s in the same direction as B C) 2.7 m/s in the same direction as A D) 1.0 m/s in the same direction as B E) 5.0 m/s in the same direction as A The magnitude of the acceleration of a planet in orbit around the Sun is proportional to: A) the mass of the planet B) the mass of the Sun C) the distance between the planet and the Sun D) the reciprocal of the distance between the planet and the Sun E) the product of the mass of the planet and the mass of the Sun

Explanation / Answer

45.

friction is internal force that will act in pair and total trque due
friction on turnable plus photograph system will be zero.

hence angular momentum will be conserved.

Ans ( d)

46.

Vcm = m1v1 + m2v2 / (m1+m2)

= (4x 2 + 8(-3)) / (4 + 8)

= -1.3 m/s

minus indicates opposite direction.

Ans(B)

47.

a = G M / r^2

Ans( B)

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