What is the translational speed of a solid ball of radius 0.5 m,that is initiall
ID: 1748684 • Letter: W
Question
What is the translational speed of a solid ball of radius 0.5 m,that is initially at rest, after it rolls 5m down a hill that isinclined at 30 degrees to the horizontal. The moment ofinertia of a solid ball about an axis through its center of mass is2/5MR2 where M is its mass and R is itsradius. (Back of the book says the answer is 5.92 m/s, but Iwould like to know how they got this answer)Also based on the above information find the rotational speed ofthe solid ball at the bottom of the hill. (Hint use V=r)
Explanation / Answer
this is a conservation of energy problem, the ball is atop a hillthat can be thought of as a triangle with an angle 300so the height is 5m(sin30) = 2.5 meters the initial gravitational potential energy (mgh) equals the finalkinetic energy due to translational and rotational motion. thus mgh = 1/2 I 2 + 1/2 m v2 mgh = 1/2 I 2 + 1/2 mr22 now we know everthing but which can be solved with algebraicmanipulation. 2 = mgh/(1/2 I + 1/2 m r2)
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