Lesson_4.3_Homework

# Lesson_4.3_Homework - (iv the angular velocity of the disc...

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Lesson 17 Homework 1. 1.2 m 32 kg 27 kg 0.4 m 5 kg The figure shows two masses 27 kg and 32 kg connected by a spring that passes over a frictionless pulley of mass 5 kg and radius 0.4 m. The 27 kg is resting on the table top and the 32 kg is 1.2 m above the table top. If the system is released, use the conservation of energy to find the speed of the 32 kg mass just before touching the table. 2. A centrifuge rotor that has a moment of inertia 4.5 x 10 -2 kg.m 2 is rotating at 10,000 rpm. How much work needs to be done to bring it to rest? 3. A park merry-go-round is a 300-kg disc of radius 2.5 m. To start it rotating, you wrap a rope around it and pull it with a force of 300 N for 15 s. Find (i) the moment of inertia of the disc? (ii) the torque generated by the applied force. (iii) the angular acceleration of the disc.
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Unformatted text preview: (iv) the angular velocity of the disc after 15 s. (v) the angular momentum of the disc after 15 s. (vi) the kinetic energy of the disc after 15 s. (vii) the angle that the disc turns in 15 s. (viii) show that the work done τθ is the same as the kinetic energy. 4. A figure skater increases her rotation rate from 1 rev every two seconds to 2 rev.s-1 . If her initial moment of inertia was 4.6 kg.m 2 , what is her final moment of inertia? How is the change accomplished? 5. A man stands with his hands on his sides on a platform that is rotating at 2.5 rev.s-1 . If the man now raises his hands to a horizontal position, the speed of rotation decreases to 1.7 rev.s-1 . (i) What is the reason for this change? (ii) By what factor has the moment of inertia of the person changed?...
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