Fred\'s ball and Barney\'s ball have the same size, but Barney\'s ball is hollow

Question

Fred's ball and Barney's ball have the same size, but Barney's ball is hollow. Betty's ball and Wilma's ball are scaled down versions of Fred's ball and Barney's ball respectively. They all place their bowling balls on the same pitch incline and release them from rest in the same time. (Select G-Greater than, L-less than, E-Equal to.) Please see diagram printed on your homework page. The order of the objects in the diagram is Fred, Betty, Barney, Wilma. The time it takes for Barney's ball to hit the pins is .... that for Wilma's ball to hit. The time it takes for Barney's ball to hit the pins is .... that for Betty's ball to hit. The time it takes for Fred's ball to hit the pins is .... that for Barney's ball to hit. The time it takes for Betty's ball to hit the pins is .... that for Wilma's ball to hit. The time it takes for Fred's ball to hit the pins is .... that for Wilma's ball to hit. The time it takes for Fred's ball to hit the pins is .... that for Betty's ball to hit. Answer: Last Answer: EEGGLL Not yet correct, tries 1/5 You need to know the formulas for the moment of inertia of a hollow ball and a solid sphere. (I for a bellow ball is 2/3 MR^2, for a solid sphere is 2/5 MR^2) But it turns out you do *not* need to know the mass of the size of any of the objects concerned in this problem! A ball of mass 2.70kg and radius 0.148m is released from rest on a plane incline at an angle theta = 41.0 degrees with respect to the horizontal. How fast is the ball moving (in m/s) after it has rolled a distanced d= 1.55m? Assume that the ball rolls without slipping, and that its moment of inetia about its center of mass is 1.80 times 10-2 kg*m2.

Explanation / Answer

Simple question about mass. Assuming the girl's balls are not *hugely* different in size from the boy's balls (so to speak), then Barney's ball will be the heaviest as it is the biggest AND is filled Wilma's ball is next heaviest, it is not the biggest, but it is filled Fred's ball is next, being biggest but hollow Betty's ball is last, being both the smallest and hollow Note if Wilma's ball is very very small, then Fred's ball might be slightly heavier, but we assume this is not the case. They're all acted on by the same forces (same friction, same gravity, etc) and they all start at the same speed (from rest), so there are no extra factors to consider. Thus we'd expect the balls speed to be ordered from fastest to slowest as: Barney, Wilma, Fred, Betty Time is, of course, related to the speed. The faster it gets there, the less time it takes. so your answers are: 1 C 2 A 3 C 4 A 5 A 6 A Note it can't be answer B - the balls are all different.

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