angular velocity?

Question

an electric saw uses a circular spinning blade to slice through wood. when you start the saw, the motor needs 2 secs of constant angular acceleration to bring the blade to its full angular velocity. of you change the blade so that the rotational mass, how long will the motor need to bring the blade to its full angular velocity?

Answer 1

using w=I*a*t
where I is the moment of inertia

A disc has I=.5*m*r^2

from the statement
w and a are are the same for both, but the mass is different
for the first m1:
w=.5*m1*r^2*a*2
for the second
w=.5*m2*a*r^2*t2

divide the two equations
t2=(m1/m2)*2



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