Answer:
The  rotational kinetic energy is  [tex]K = 2116.3 \ J[/tex]
Explanation:
From the question we are told that
  The moment of inertia  is  [tex]I = 0.35 \ kg \cdot m^2[/tex]
  The number of revolution is N  =  70 revolution
   The  time taken is  t  =  4.0  s
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Generally the angular velocity is mathematically represented as
   [tex]w = \frac{2 \pi N }{t }[/tex]
substituting values
   [tex]w = \frac{2* 3.142 * 70 }{4 }[/tex]
    [tex]w = 109.97 \ rad/s[/tex]
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The rotational kinetic energy K i mathematically represented as
    [tex]K = \frac{1}{ 2} * I * w^2[/tex]
substituting values
    [tex]K = \frac{1}{ 2} * 0.35 * (109.97)^2[/tex]
    [tex]K = 2116.3 \ J[/tex]
