10. In practicing for the 2018 Winter Olympics, which is to take place in a myst

Question

10. In practicing for the 2018 Winter Olympics, which is to take place in a mysterious far off land known as "Korea", Park So-Youn performs a spin on ice with her arms outstretched, what happens when she er to brings her arms close to her body? A) Her angular momentum increases and her kinetic energy decreases. B) Her angular momentum remains the same and her kinetic energy increases. C) Both her angular momentum and kinetic energy remain the same. D) Her angular momentum remains the same and her kinetic energy decreases. Ju 11. A bullet hits a wood rod that is pivoted on its left end shown. Consider 3 different cases i) the bullet hits the rod and bounces off the rod and rebounds in the opposite direction, ii) the bullet becomes embedded with the rod and swings with the rod and ii) the bullet goes through the rod. In which case does the rod have the greatest angular velocity after interacting with the bullet? A) When the bullet bounces off the rod and rebounds. B) When the bullet is embedded in the wood rod. C) When the bullet goes through the rod. D) The rod will have the same angular velocity in all 3 cases.

Explanation / Answer

(10) Option (C) Bothe her angular momentum and kinetic energy remain the same, is the correct option.

Explanation -

Angular momentum in the case of circular motion remains conserved. Further, since there is no loss of energy in the given condition, so kinetic energy will also be constant.

(11) Option (B) 'When the bullet is embedded in the wood rod, is the correct option.

Explanation -

When the bullet is embedded in the the wooden rod, it completely transfers all of its energy into the wodden rod. In the other two cases, complete conversion of kinetic energy of the bullet is not happeneing.

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