V (vector) = ω (vector) ×r (vector)

ω (vector) =2πk, r (vector) =3i+4j+5k.

V (vector) = ω (vector) ×r (vector) = 6 π j-8 π i.

Size: 10π cm/s

Method 2: The circular motion radius of a point is the projection of the position vector on the xy plane, with a length of 5cm and an angular velocity of.

2π radian per second, according to the relationship between linear speed and angular speed, the speed is10 π cm/s.