Concept of Clocks and Tricks

CLOCKS 

1.  Clock Hands :

A clock has 2 hands. One hour hand and one minute hand.

a.   An hour hand takes 12 hours to move 1 complete round.
i. e. It takes 12 hours or 720 minutes to cover 360 degree.
i. e. In 1 minute the hour hand travels  by half degree.


b.   A minute hand takes 1 hour to move 1 complete round.
i. e. It takes 1 hour or 60 minutes to cover 360 degree.
i. e.  In 1 minute the minute hand travels by 6 degree.

2.  Formulae :

  a.  Hour Hand  1 min =  half degree.
  b.  Minute Hand 1 min = 6 degree. 

  c.  The general formula to find the angle between the HH and the MH is:

Angle = 30 H - 11/2 M.

Ex: a.  When time is 4:33, H=4 and M=33.
      b.  When time is 12:30, H= 0 and M =30.

3.  Minute Spaces:

The face or dial of watch is a circle whose circumference is divided into 60 equal parts, called minute spaces.

Hour Hand and Minute Hand:

i.
A clock has two hands, the smaller one is called the hour hand or short hand while the larger one is called minute hand or long hand.

 i i. In 60 minutes, the minute hand gains 55 minutes on the hour on the hour hand.

i i i.
In every hour, both the hands coincide once.

i v.
 The hands are in the same straight line when they are coincident or opposite to each other.


v.   When the two hands are at right angles, they are 15 minute spaces apart.


vi.  When the hands are in opposite directions, they are 30 minute spaces apart.


vii.  Angle traced by hour hand in 12 hrs = 360°


viii.  Angle traced by minute hand in 60 min. = 360°.


i x.  If a watch or a clock indicates 8.15, when the correct time is 8, it is said to be 15 minutes too fast.


x.  On the other hand, if it indicates 7.45, when the correct time is 8, it is said to be 15 minutes too slow.