Question

A body completes one round of a circle of radius $R$ in $20$ second. The displacement of the body after $45$ second is :

• A. $\frac{R}{\sqrt{2}}$
• B. $\sqrt{2}R$
• C. $2\sqrt{2}R$
• D. $2R$

Answer 1

Answer: (B)

$\sqrt{2}R$

Assuming uniform motion, after 45 seconds body will have finished $\frac{45}{20}=2.25$ rounds, i.e., if it starts from A it will be at B after 45 seconds.

Now, displacement $AB$= $\sqrt{R^2+R^2}=\sqrt{2}R$