First of all, we need to convert the angular speed from rev/min into rev/s:
[tex] \omega_f=300 rev/min=5 rev/s [/tex]
The angular acceleration is the variation of angular speed divided by the time:
[tex] \alpha=\frac{\omega_f-\omega_i}{t}=\frac{5 rev/s-0}{2 s}=2.5 rev/s^2 [/tex]
And this is constant, so we can use the following equation to calculate the angle through which the engine has rotated:
[tex] \theta(t)=\frac{1}{2}\alpha t^2 =\frac{1}{2}(2.5 rev/s^2)(2 s)^2=5 rev [/tex]
so, 5 revolutions.
