Question

The minute hand of a watch is 1.5 cm long. How many cm. does its extremity move
in 40 minutes ?
​

Answer 1

Answer:

We know that l=rθ

Hence r=1.5cm

Now we know that minute hand make 1- a revolution in 1-hour

Hence we can say

minute hand completes 360

∘

in one hour

So degree complete in

1min=

60

360

So degree complete in

40min=

60

360

×40

=240

∘

Hence θ=240

∘

Radian measure =

180

π

×θ

=

180

π

×240

=4π/3

Now l=rθ

l=1.5×4π/3

l=0.5×4π

=2π

=2×3.14

l=6.28cm