Question

An athlete completes 1 round of circular track of radius 105 m in 10 s .what will be the distance covered and the displacement after 1 min 20 s.

Answer 1

Distance : 2200 m and displacement is 200 m

detail explanation:

one round circular track of 200 m dia in 40 sec

distance travelled in 2 min 20 sec = distance travelled in 120+20 = 140 sec

one complete round takes 40 sec then how many rounds he can do in 140 sec = 3.5 rounds nothing but 7/2

circumference of circle = distance travelled to complete one circular track = 2 x pie x radius means pie x diameter

7/2 rounds distance = 7/2 * pie * dia = 7/2 * 22/7 * 200 = 2200 m distance

displacement means shortest distance, though he travelled 3.5 rounds but displacement is diameter only

so displacement is 200 m

Answer 2

Given:

The athlete completes one round of circular track of radius 105 m in 10 s

The athlete had to cover the circumference of the circle.

We know that :

Circumference = π d

d = r * 2

= 105 m *2

C ==> π * 105 m * 2

==> 22 / 7 * 210 m

==> 22 * 30

==> 660 m

So the athlete covers 660 m in 10 s

1 min 20 s

==> 60 + 20 s

==> 80 s

So in 80 s the athlete will cover 660 m * 80 s / 10 s

==> 660 m * 8

==> 5280 m

The athlete will cover 5280 m

But you asked for displacement.

The athlete completes a round for every 10 s

After 1 min 20 s that is 80 s

The athlete would complete 8 laps

So it would come back to its original position.

So the displacement would be zero.

The displacement is zero.

Your answer is zero

Hope it helps you

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