Question

if the minute hand of a wall clock is 20 cm long then what will be the distance and displacement covered by tip of minute hand from 9 a.m. to 9:30 a.m.

Answer 1

length of minute hand=20 cm
from 9:030 to 9:30 it will form a semicircle.
distance=circumference of semi circle=2πr/2
=2×22/7×20=8800/7= 1257/2=628.5 cm

displacement=diameter of semicircle
diameter=2×radius= 2×20=40 cm
hope it helps:)

Answer 2

Length of the minute hand = 20 cm = 0.2 m

Let the positions be like :

(See attachment for clearance)

From 9 :00 am to 9:30 am , the minute hand of the clock moves from position A to position C along the position C along the path ABC .

So ,

a) The distance ABC covered by minute hand =

Length of circular arc ABC =

πl = (22/7) × 0.2 m = 0.63 m

The required distance = 0.63 m

b) The displacement of the minute hand =

length of the chord AOC =

2l = 2 × 0.2 = 0.4 m

The required displacement = 0.4 m