UNIVERSITI TEKNIKAL MALAYSIA MELAKAFAKULTI KEJURUTERAAN MEKANIKAL

DMCG 1323 – DYNAMICSTUTORIAL 3

1. In the braking test of a sports car its velocity is reduced from 110 km/h to zero in a distance of 51 m with slipping impending. Knowing that the coefficient of kinetic friction is 80 percent of the coefficient of static friction, determine (a) the coefficient of static friction, (b) the stopping distance for the same initial velocity if the car skids. Ignore air resistance and rolling resistance.Answer: (a) μs = 0.933 (b) 63.8m

2. A 40-kg package is at rest on an incline when a force P is applied to it. Determine the magnitude of P if 4s is required for the package to travel 10 m up the incline. The static and kinetic coefficients of friction between the package and the incline are 0.30 and 0.25, respectively.Answer: P = 612 N

3. Boxes A and B are at rest on a conveyor belt that is initially at rest. The belt is suddenly started in an upward direction so that slipping occurs between

the belt and the boxes. Knowing that the coefficient of kinetic friction between the belt and the boxes are (μk)A = 0.30 and (μk)A = 0.32, determine the initial acceleration of each box.Answer: aA = 0.304 m/s2

15o ccw, aB = 0.493 m/s2 15o ccw.

4. A 250-kg crate B is suspended form a cable attached to a 20-kg trolley A which rides on an inclined I-beam as shown. Knowing that at the instant shown the trolley has an acceleration of 0.4 m/s2 up to the right, determine (a) the acceleration of B relative to A, (b) the tension in cable CD.Answer: aB/A = 0.363 m/s

TCD = 1145 N

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