(a) What is the angular velocity of the two after the collision? rad/s (b) What
ID: 1372909 • Letter: #
Question
(a) What is the angular velocity of the two after the collision?
rad/s
(b) What is the kinetic energy before and after the collision?
KEi
KEf
KEi
= JKEf
= J The figure shows an overhead view of a 2.70-kg plastic rod of length 1.20 m on a table. One end of the rod is attached to the table, and the rod is free to pivot about this point without friction. A disk of mass 44.0 g slides toward the opposite end of the rod with an initial velocity of 20.5 m/s. The disk strikes the rod and sticks to it. After the collision, the rod rotates about the pivot point. (a) What is the angular velocity of the two after the collision? rad/s (b) What is the kinetic energy before and after the collision? KEi = J KEf = JExplanation / Answer
apply the law of conservation of angular momentum
Li = mvL
so final ang moemtum Lf = IW
where Moment of Inertia here I = mL^2 + (1/3 ML^2)
so
W = (mv)/(m+ M/3)L)
W = (2.7 * 20.5)/(2.7 + 0.044/3) * 1.2
W = 180.30 rad/s
-----------------
apply Initial KE = 0.5 mv^2
kEi = 0.5 * 2.7 * 20.5 *20.5
KEi = 567.3375 J
-----------------------------
KEf = 0.5 Iw^2
KE f = (0.5)*(2.7 * 1.2*1.2) +(1* 0.044 * 1.2*1.2/3) * 567.33*567.33)
KEf = 6800 Joules
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