Question

The seconds needle of a clock is 7cm long. How much distance is covered by its outer edge in 24 hours. (Hint: there are 1440 minutes in 24 hours

Answer 1

Answer:

Distance covered by seconds needle in 24 hours is 633.6 m

Step-by-step explanation:

Given that seconds needle of a clock is 7 cm long

Distance covered by seconds needle in 1 minute is the circumference of circle of radius 7 cm.

We know circumference of circle is calculated as

$C=2\times \pi \times R$

where R = Radius of circle

Here, R = 7 cm

Thus, circumference is

$C = 2 \times \pi \times 7\\\\C = 2 \times \frac{22}{7} \times 7\\\\C = 2 \times 22\\\\C = 44\hspace{0.1cm}cm$

Thus, the distance covered by seconds needle in 1 minute is 44 cm

Distance covered by seconds need in 24 hours is $24 \times 60 \times 44 = 63360\hspace{0.1cm}cm = 633.6\hspace{0.1cm}m$

Answer 2

Answer:

the correct answer is 63360 cm or 633.60 m.

Step-by-step explanation:

the second needle completes

1 minute = 1 revolution

24 hours =? revolutions

we know that

24 hours = 24 *60 minutes = 1440 minutes

therefore

24 hours = 1440 minutes=1440 revolutions

as the second needle completes 1 revolution in 1 minute .2 revolution in 2 minutes,3 revolution in 3 minutes and hence  1440 revolution in 1440 minutes.

now

the distance covered in 1 revolution=circumference (c) of the clock

c = 2 π r

c = 2 * 22/7 * 7

c = 44 cm

hence the distance covered in 24 hours(1440 revolutions) = 24 * 1440

                                                                                                 = 63360 cm Ans

1 cm = 1/100 meter             as centi = 1/100

therefore

63360 cm=63360 * 1/100 m

                 = 633.60 m ans.