Question

Question #d8ba2

Answer 1

I got `6.4revs`

Explanation:

I would use the general relationship for rotational motion (analogous to the linear one):
`omega^2=omega_0^2+2alphatheta`
where:
`omega=` angular velocity (initial and final, with `omega=0` the final one);
`alpha` is angular acceleration;
`theta` is the angle in radians.
We get:
`0=20^2-2*5*theta` as it is slowing down `alpha<0`;
rearranging:
`theta=400/10=40rad`
Giving:
`40/(2pi)=6.36~~6.4revs`