http://www.physics.qc.edu/files?454 please i need help in this its due in just a

Question

http://www.physics.qc.edu/files?454
please i need help in this its due in just a few hours.

a) In procedure 1: when you drop the mass holder, the system rotates at angular acceleration ?. If you wrapped the string around a larger diameter pulley and dropped the mass holder, the acceleration of the system would be
more than ?
less than ?
exactly ?

b) In procedure 2 trial 1: suppose the system is rotating clockwise when the metal disk is dropped on it. The direction of the frictional force is
counter-clockwise on the disk, clockwise on the system
counter-clockwise on the disk zero on the system
clockwise on the disk and the system
zero on the disk and the system
clockwise on the disk, counter-clockwise on the system
zero on the disk, counter-clockwise on the system
clockwise on the disk, zero on the system
counter-clockwise on the disk and the system
zero on the disk, clockwise on the system

c) In procedure 2 trial 1: suppose the coefficient of friction between the metal disk and the system is ?. If the coefficient of frction is increased, what will happen to ?f, the final angular speed of the system, and ?E, the energy lost from the system during the time the metal disk reaches the same speed as the system?
?f remains the same, ?E increases
?f decreases, ?E remain the same
?f increases, ?E increases
?f decreases, ?E decreases
?f increases, ?E remain the same
?f decreases, ?E increases
?f increases, ?E decreases
?f and ?E remain the same
?f remains the same, ?E decreases


NOTE: These numbers are not realistic.

Suppose that, in procedure 1, you measured the moment of inertia of the system as I = 9.82 kg-m2. Assume the diameter of the pulley around which you wrap the string is d = 3.07 cm.

a) In trial 1:the system is initially spinning at angular speed ?o = 9.44 rad/s. After you drop a disk of mass 727 g on it, the system rotates at ?f = 8.63 rad/s. Find:
- the moment of inertia of the disk: ------

kg-m2
- the radius of the disk: ------m

b) In trial 3: suppose the system is initially spinning at angular speed ?o = 2.73 rad/s. After you drop a cube of mass 764 g on it, the system rotates at ?f = 2.21 rad/s. Find:
- the moment of inertia of the cube: ------kg-m2
- the length of one side of the cube: ------cm

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