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# Angular velocity, Final temperature

1) A boxer is struck by an opponent causing him to rotate about a vertical axis with an angular velocity of one revolution per second while his arms are extend horizontally with a 12-kg glove on each hand. He drops his hands to his sides hoping that the increase in angular velocity will cause the next blow to glance off him. If the moment of inertia of his body remains approximately constant at 6.0 kg m^2 and the distance of the masses from the axis changes from 1m to 0.1 m, what will be his final angular velocity (in rev/s)?

2) 2.5 moles of a mono-atomic ideal gas undergo a reversible adiabatic expansion from an initial pressure of 320 kPa and initial volume of 36 L to a final volume of 60 L. What is the final temperature?

3) A mass of iron traveling at 200 m/s slams into solid wall and comes to a rest. If all of the kinetic energy lost in the collision becomes internal energy of the iron, what is the increase in temperature of the iron? The specific heat of iron is 0.a07 cal/ (g.C).

#### Solution Preview

Problem 1 deals with conservation of angular momentum and calculation of moments of inertia.
Problem 2 deals with dQ=0=dU+dW and ideal gas relations.
Problem 3 deals with conservation of energy and Cv(T2-T1) = KE.

1) This is an example of conservation of angular momentum Iw = Iowo.

The moment of inertia of his gloves is what changes here. Consider a body consisting ...