Question

Milkha singh can cover one round of a circular park
in 40 second, After 1 minute and 40 second, he
will cover a distance and dispalcement respectively:-
(R = Radius of circle) :-
(1) Zero, Zero
(2) 41R, R
(3) 5R, 2R
(4) 61R, 2R​

Answer 1

Answer:

3] 5R' 2R

Explanation:

circumference of a circle = 2πr   40sec + 40sec+ 20sec= 2 1/2 rounds

1min=60sec + 40=100sec     1 round= 40 sec

= 2×π×2+1/2  => 2×π×5/2 => 5πR

Answer 2

He covers 10πR and 0 as distance and displacement respectively.

Given,

Round made by Milkha Singh=1

Time in which he can make a round of the park=40 seconds.

To find,

the distance and the displacement that he makes after 1 minute 40 seconds.

Solution:

• Distance is the complete length of the path between any two points.

• T is the radius of the circular park.
• Displacement is the direct length between any two points when measured along the minimum path between them.

As he covers a distance of 2πR in 40 seconds.

1 minute 40 seconds=(60+40)seconds

1 minute 40 seconds=200 seconds.

His speed while making the first round,

$Speed=\frac{Distance}{Time} \\Speed=\frac{1X2\pi R}{40}\\Speed=\frac{2\pi R}{40}.$

The distance that he covers in 1 minute and 40 seconds,

$Speed=\frac{Distance}{Time} \\\frac{2\pi R}{40}=\frac{Distance}{200}\\Distance=\frac{2\pi R}{40}X200\\Distance=2\pi RX5\\Distance=10\pi R.$

He covers 10πR in 1 minute and 40 seconds.

2πR makes one round, so 10πR will make 5 rounds.

This means that Milkha Singh returned to the same point from where he started.

Thus, his displacement will be 0.

The distance and the displacement are 10πR and 0 respectively.

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