Question

A body completes one round of a circle of radius R in 20 seconds the displacement of the body after 45 seconds is

Answer 1

Answer:

zero

Explanation:

displacement is the shortest distance between the original and final place which is zero in circular direction

Answer 2

Answer

r√2 units is the displacement.

Explanation :

Given,

• It takes 20 seconds for one complete revolution of circle of radius r.

• It's displacement after 45 seconds ><

Let's split 45 into sum of 3 numbers

$\implies \: 45 = 20 + 20 + 5$

we know that displacement of a body when it travels for 20 seconds is zero.

• Because, when a body reached its initial position at final then displacement becomes zero.

Now here,

• For its 40 seconds of journey it's displacement = 0

Displacement in 5 sec :

• It took 20 seconds to give one complete revolution.

• >> For 5 secs it completes 1/4 th the journey.

so, now we need to find the displacement of quarter of circle,

• Refer above attachment.

Here AB is displacement.

$\implies \: AB \: = \sqrt{ {r}^{2} + {r}^{2} }$

$\implies \: AB \: = \sqrt{ 2{r}^{2} }$

$\implies \: AB \: = r \sqrt{2} \: units$

Therefore, the total displacement of body

= 0 + r√2

= r√2