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Unformatted text preview: \‘ﬂ. ME 240(23): Quiz 2 ‘
Fall 2010 Name: go; 0 ”r7 d AJ Section# Problem 1. (20 points)
1 1. Points A and B are ﬁxed on the disk. A has a velocity VA and the disk has a constant angular velocitya). Which of the unit vectors represents the direction of relative velocity vBlA ? .e 6:2
1.2.What vector represents the direction of relative acceleration Zia/,4 ? é]
1.3.The crate AB is supported by 2 cables from a trolley. The crate is not
currently swaying, such that you know the crat is
.Accelerating to the right b. Not accelerating .
c. Accelerating to the left 1.4. How do the tensions in the 2 cables compare? TA< TB
c. TA>T3 1.5.The upper rack is ﬁxed. The lower rack is moving to the right with a speed
of 2 m/s. The speed of the center of the pinion is: 110:1 m/s
c. vo=4 m/s 1.6.The pinion has a radius r=0.25 In. The angular velocity of the pinion is a. sz m/s
® 60:4 m/s
c. 028 m/s 1.7. The parallel axis theorem can be used to
a. Relate mass moments of inertia about any two points on a rigid body
Relate mass moments of inertia about the center of mass and another point on a rigid body
Compute the center of mass of a system made up of multiple rigid bodies 1.8. Slider A has a constant relative speed at > O at a position X=0 in a disk that is Y rotating with angular velocitya). At that instant, the velocity of A is
a. zero ' in the +X direction
c. in the +Y direction 1.9. Slider A has a constant relative speed 3': > O at a position X20 in a disk that is rotating with angular velocitya). At that instant, the acceleration of slider A is
a. zero b. in the +X direction
@ in the +Y direction l.lO.The disk is attached to the bar with a ﬁictionless pin. The system is released from rest resulting in
a. Clockwise angular'acceleration of the disk
b. Counterclockwise angular acceleration of the disk
C? No angular acceleration of the disk Problem 2 (40 points). The quick return reciprocating mechanism consists of a:
a disk pinned at its center A that rotates with a constant angular velocity (DAB
- slotted arm CD that' IS pinned at C a bar that can translate horizontally Within the guides at E and F.
As the disk rotates, the peg at 3‘ moves Within the slotted arm CD. This causes CD to rock back and forth, which advances and returns the reciprocating bar due to changing distance between C and B.
Given: coAB=120 rpm, R=O.2 m, h=0.4 In, and d=0.12 m
a) At position 1, determine the angular velocity 6CD and the velocity of the bar 17W b) At positipg, 2, what' IS the velocity of B relative to a reference frame ﬁxed 1n CD i. e y. 7 POSitiOIl 1 position 2 A
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has negligible mass and slides without friction. The system is released from rest with the bar at an angle (9:30°. Immediately after release, determine: (a) The angular acceleration a of the rod (indicate direction) (b) The normal reaction force N acting on the bar at B 9
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