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Mastering CH 7:

Center of Mass

Physics 121

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· Chapter 7 J -25. (II) A ball of mass 0.440 kg moving east ( + x direction)

with a speed of 3.80 m/s collides head-on with a 0.220-kg ball at rest. If the collision is perfectly elastic, \vhat \ViU be the speed and direction of each ball after the collision?

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47. (II) The CM of an empty 1250-kg car is 2.40 m behind the front of the car. How far from the front of the car will the CM be when two people sit in the front seat 2.80 m from the front of the car, and three people sit in the back seat 3.90 m from the front? Assume that each person has a mass of 65.0 kg.

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~ -~ !l~ ~SSIONALS Chapter 7

48. (II) Three cubes, of side l0 , 2£0 , and 3£0 , are placed next to one another (in contact) with their centers along a straight line as shown in Fig. 7-38. What is the position, along this line, of the CM of this system? Assume the cubes are made of the same uniform material.

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fits\ I ~ NGIN EE RS ~SSIOMALS l Chapter 7 J

50. (III) Determine the CM of the uniform thin L-shaped con­struction brace shown in Fig. 7-40.

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FIGURE 7-40 Problem 50. This L-shaped object has uniform thickness d (not shown).

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