Question

The speed of a moving bullet can be determined by allowing the bullet to pass through

two rotating paper disks mounted a distance
97 cm apart on the same axle. From the
angular displacement 12.9◦
of the two bullet holes in the disks and the rotational speed
1319 rev/min of the disks, we can determine
the speed of the bullet.
What is the speed of the bullet?
Answer in units of m/s.

Answer 1

f = 1219/min = 1219 / 60 / sec = 20.32 / sec

T = 1/f = 1 / 20.32 = .04922 sec period of 1 revolution

t = 12.9 / 360 * .04922 = .001764 sec time to pass between disks

V = S / t = .97 m / .001764 = 550 m/sec