Question

plz answer this class 9 ch motion ​

Answer 1

If he covers 200 m in 40 second
Then he is covering 200/40
= 5m in every second
So in 2 min 20 sec or 140 sec(1 min=60sec)

He will cover = 140*5

= 700 m


And the displacement is 0 as he is running on a circular track and he comes back to the starting point after running




Hope it helps





Please mark this answer as brainliest

Answer 2

Given:

Diameter of Track, D= 200 m

Time taken by athlete to complete 1 round of track, t= 40 s

To Find:

​Distance covered and the displacement at the end of 2 min 20 s

Solution:

We know that,

• $\pink{\boxed{\bf{Radius=\frac{Diameter}{2}}}}$

• $\purple{\boxed{\bf{Circumference=2\pi r}}}$

where r is radius

• Distance is the length of actual path covered by body

• Displacement is the shortest distance between starting and final position

$\rule{190}{1}$

Given time t is

$\longrightarrow\rm{t=2\:min\:+20\:s}$

$\longrightarrow\rm{t=2\times60\:s\:+20\:s}$

$\longrightarrow\rm{t=120\:s\:+20\:s}$

$\longrightarrow\rm{t=140\:s}$

$\rule{190}{1}$

Now,

Rounds completed by athlete in 40s= 1

Rounds completed by athlete in 1s= $\dfrac{1}{40}$

Rounds completed by athlete in 140s=$\rm{\dfrac{1}{40}\times140}$

or

Rounds completed by athlete in 140s=$3.5$

That means athlete covers 3 and a half round in 140s

$\rule{190}{1}$

Let the radius of circular track be r

So,

$\longrightarrow\rm{r=\dfrac{D}{2}}$

$\longrightarrow\rm{r=\dfrac{200}{2}=100\:m}$

$\rule{190}{1}$

Let the circumference of circular track be C

So,

$\longrightarrow\rm{C=2\pi r}$

$\longrightarrow\rm{C=2\times\dfrac{22}{7}\times100}$

$\longrightarrow\rm{C=\dfrac{4400}{7}\:m}$

$\rule{190}{1}$

Let the distance covered by athlete be d and displacement of athlete be d'

So,

$\longrightarrow\rm{d=3C+\dfrac{C}{2}}$

$\longrightarrow\rm{d=\dfrac{6C+C}{2}}$

$\longrightarrow\rm{d=\dfrac{7C}{2}}$

$\longrightarrow\rm{d=\dfrac{\cancel{7}\times\dfrac{4400}{\cancel{7}}}{2}}$

$\longrightarrow\rm{d=\dfrac{4400}{2}}$

$\longrightarrow\rm\green{d=2200\:m}$

Also,

Since, after covering 3 and half rounds final position of athlete is diametrically opposite to starting position

Therefore,

$\longrightarrow\rm{d'=D}$

$\longrightarrow\rm\green{d'=200\:m}$

Hence, distance covered by athlete is 2200 m and displacement of athlete is 200 m.