Initial angular speed of the bullet is 2200 rad/s
after some time the angular speed of bullet is decreased and it rotates through 480 revolutions in 1.4 s
so the angle revolved by the bullet is
[tex]\theta = 2 N\pi[/tex]
[tex]\theta = 2*480*\pi= 3016 radian[/tex]
now the angular acceleration is given as
[tex]\theta = \omega_0*t +\frac{1}{2}\alpha t^2[/tex]
[tex]3016 = 2200* 1.4 + \frac{1}{2}*\alpha* 1.4^2[/tex]
[tex]3016 = 3080 + 0.98 \alpha[/tex]
[tex]\alpha = - 65.3 rad/s^2[/tex]
