Question

the minute hand of a clock is 7 cm long. find the displacement & distance covered by it from 9:00 a.m. to 9:30 a.m

Answer 1

Answer:

14 and 22 cm.

Explanation:

Since, the clock is moved from 9:00 to 9:30, the minute arm has traveled and completed a semi circle to reach 9:30. So, the the distance covered by the minute arm will be the arc from 9:00 to 9:30. The displacement will be the diameter of the swept area of the minute arm which will be 14 cm,

The, distance will be π*r where r is the radius or the length of the minute arm.

On solving we will get distance to be 22/7*7 = 22 cm.  

Answer 2

Answer:

The displacement is 14 cm and the distance is 21.98 m approximately taken as 22 m.

Explanation:

The clock has the minute hand with the length of 7 cm which moves from 9 am to 9 : 30 am, the distance covered and the displacement covered will be calculated as follows –

The displacement is the measure of the shortest distance between the two points of travel irrespective of the path followed.

Here, the minute hand initially is at 9 : 00  

And finally at 9 : 30  

So the shortest distance will the twice of the length of the minute hand as it fully stretches on either side of the clock.

Displacement = twice length of minute hand

$\begin{array}{c}{\text {Displacement}=2 \times \text {length}} \\ {\text {Displacement}=2 \times 7}\end{array}$

Displacement = 14 cm

Distance is the measure of actual length covered in the total journey.

Here, distance is half of the circumference of the clock as travelled for 30 minutes.

Distance = circumference of half clock

Distance = circumference of half circle

$\begin{aligned} \text {Distance} &=\pi \times \text { radius } \\ \text {Distance} &=\pi \times \text {length of minute hand} \end{aligned}$

Distance = 3.14 $\times$7

Distance = 21.98  m

Or Roughly Distance = 22 m