# Physics

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A constant torque of 22.9 N·m is applied to a grindstone whose moment of inertia is 0.168 kg·m2. Using energy principles, and neglecting friction, find the angular speed after the grindstone has made 17.1 rev, assuming it started
from rest.

• Physics -

M=Iε
ε=M/I = 22.9/0.168 = 136.3 rad/s²
2πN=2πn₀t + εt²/2
2πn=2πn₀ + εt
n₀=0 =>
2πN= εt²/2
2πn= εt => t=2πn/ε
N= πn²/ε
n=sqrt {εN/π}=
=sqrt{136.3•17.1/3.14}=27.24 rev/s

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