question_answer

If a boy swings in a circle so the minimum and maximum height from ground is 3 m and 6 m, then, its maximum velocity is:

A) \[5\sqrt{2}\,m/s\]

B)  \[2\sqrt{5}\,m/s\]

C)  \[3\sqrt{5}\,m/s\]

D)  \[5\sqrt{3}\,m/s\]

Correct Answer: D

Solution :

 Key Idea: Maximum velocity at lowest point is V5 times maximum velocity at highest point. Diameter AB of circle is 3m Therefore, radius \[r=\frac{3}{2}m\] velocity at \[A(v)=\sqrt{5gr}\] Given, \[g=10\,m/{{s}^{2}},r=\frac{3}{2}m\] \[\therefore \]\[v=\sqrt{5\times 10\times \frac{3}{2}}=5\sqrt{3}\,m/s\]