Question

A student ties a stone to a thread of length 1 m and starts swinging it in a circular
motion. The stone completes 20 rotations in 10 seconds. With what speed the stone is
moving?

(a)π m/ sec
(b)2π m/ sec
(c)4π m/ sec
(d)8π m/ sec​

Answer 1

Given:

A student ties a stone to a thread of length 1 m and starts swinging it in a circular motion. The stone completes 20 rotations in 10 seconds.

To find:

Linear speed of stone ?

Calculation:

• Circumference = 2πr = 2π metres.

So, total distance travelled :

$\therefore \: d = 20 \times 2\pi$

$\implies \: d = 40\pi \: m$

Now, linear speed will be :

$\therefore \: v = \dfrac{d}{t}$

$\implies \: v = \dfrac{40\pi}{10}$

$\implies \: v = 4\pi \: m/s$

So, linear speed is 4π m/s.

Answer 2

Answer:

speed = 4$\pi$ m / s

Explanation:

circumference =2 $\pi$r

distance = 6 $\pi$r

time=10sec

speed=6 m/ s

distance = speed and time

6 x 22/7 x r = 10 x 6x 60

3r=600

r=600/3

r=200