A disk shaped grindstone of mass 3.0kg and radius of 8.0 cm isspinning at 600 re

Question

A disk shaped grindstone of mass 3.0kg and radius of 8.0 cm isspinning at 600 rev/min. After the power is shut off, a mancontinues to sharpen his axe by holding it against the grindstoneuntil it stops 10 s later. What was the stone's initial kineticenergy when the power was turned off?

A constant torque of 15 N per meter acts for 3.0 s on a system ofmas 2.0 kg. The change in angular momentum of the system duringthis period of time is ?

The center of gravity and the center of mass coincide if (a) thebody is in rotational equilibrium (b) the body is in translationalequilibrium (c) the acceleration due to gravity is constant overthe body (d) the body is in both translational and rotationalequilibrium (e) any forces acting accelerating the body areconstant

Explanation / Answer

a.) KE = 1/2I2 =1/2(1/2mr2)2= 1/4(3 kg)(0.08 m)2(20rad/s)2 ˜ 18.95 J b.) L = x t = (15 N/m)(3 s) = 45 N s/m c.) (c), another way of saying "in a uniform gravitationalfield"

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