Question

A watch a second hand $2cm$ long. Calculate :
i) the speed of the tip of the second hands
ii) the velocity of the tip at $t=0$ and $t=15$ seconds.
iii) change in velocity from $t=0$ to $t=15$ seconds.

Answer 1

It's average velocity will be zero as there will be no displacement after one rotation. But if you are asking about the speed then here is your solution :-

Distance travelled by tip in one rotation = 2pi*r

= 2 * 22/7 * 2 = 88/7 cm

Time = 1 min = 60 seconds

So, Speed = 88/(60*7) = 88/420 cm/sec = 0.209 cm/sec or 0.21 cm/sec