The second's hand of a watch is 2cm long, the speed of the tip of this hand is
A. 0.21 cm/s B. 2.1 cm/s C. 21.0 cm/s
I think we can solve this question by calculating angular velocity.
The circular path of the tip of the watch is, d = 2 × π × r = 2 × 3.14 × 2 = 12.56 cm
The time in which the tip covers one revolution, t = 60 s
The speed of the tip is,v = 12.56/60 = 0.21 cm/s
Correct option is A.
Yes, you can calculate the same by first finding the angular velocity.
Angular velocity, ω = 2π/t (t = 60 s)
Speed, v = rω = 2πr/t
Which again gives us the same result.