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Unformatted text preview: Name: RIN: Problem #1 (30 points) (13.129) A tractor—trailer rig with a 2000-kg tractor, a 4500—kg trailer, and a 3600-kg trailer is traveling on a
level road of 90 km/h. The brakes on the rear trailer fail and the antiskid system of the tractor and
front trailer provide the largest possible force which will not cause the wheels to slide. Knowing the
coefﬁcient of static friction is 0.75, determine the force in the coupling between the two trailers during the time it takes the rig to come to a stop. Assume that the force exerted by the coupling on each of the
two trailers is horizontal. . “’1 .. g 'f , I, I}
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I/i , // y “,1, ,, J Name: RIN: I) ,//“ (H) m Problem #2 (35 points, 7 points each part) 14.46 Four small disks A, B, C, and D can slide freely on a
frictionless, horizontal surface. Disks B, C, and D are
connected by light rods and are at rest in the position shown
when disk B is struck squarely by disk A which is moving
to the right with a velocity v0=(12 m/s)i. The masses ofthe
disks are mA=mB=mc =7.5 kg, and Inn: 15 kg. The
velocities ofthe disks immediately after impact are VA:0,
VB: (3.5 m/s)i, vc=vci, and vD=vDi. Find: a) the initial linear momentum Li. b) the initial angular momentum about the origin H01. 0) the linear momentum L2 just after the collision in terms
ofthe unknown velocities vc and V1). (1) the velocities vc and V[). c) the work done during the collision U14. 1 Name: RlN: Problem #3 (35 points, 7 points each part) 15.56 Rod AB is attached to a collar A and is ﬁtted with a small wheel
at B which rolls on a circular surface. When 6 = 60°, the velocity (j * "\-~\\ _ . J ‘ ofthe collar is 1.2 ft/s downward and the angle OCH "2: = 35.3 "
’ﬂv/ 1') “125m / I determine at that instant, (a) the angular velocity of rod AB, ([2) \ . \"""/ the velocity of point B. The velocity of the roller B is VB = V}; e,,
,\i "H‘ m “L // ' f, and the angular velocity ofthe rigid body AB is (0k. Find
‘ a. y/ pl, a) the velocity VA?' ’ i \ ) / i b) the unit vector indicating the velocity ofthe roller el.
)9 A/(; Tn / g c) the position vector rA/B. ,-
L / / / , V d) the relative velocity VM; in terms ofthe unknown (1).
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‘ r h» c) the velocity magnitude VB and the angular veIOCIty a). , /
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This note was uploaded on 04/06/2009 for the course ENGR 2090 taught by Professor Johntichy during the Spring '09 term at Rensselaer Polytechnic Institute.
- Spring '09