A) 2 cm
B) \[\frac{10}{3}\,cm\]
C) \[\frac{15}{4}\,cm\]
D) \[\frac{18}{3}\,cm\]
Correct Answer: A
Solution :
Key Idea: Energy of body at A is only potential and at B it is only kinetic. Body possess potential energy due to its, height h, this potential energy is used in given kinetic energy to the body \[\therefore \] \[mgh=\frac{1}{2}mv_{B}^{2}\] Where, \[{{v}_{B}}\]is velocity at B. \[\therefore \] \[{{v}_{B}}=\sqrt{2gh}\] Also we know that to complete the vertical circle of radius R \[{{v}_{B}}=\sqrt{5gR}\] Equating the two expressions, we get \[\sqrt{5gR}=\sqrt{2gh}\] \[\Rightarrow \]\[R=\frac{2}{5}h=\frac{2\times 5}{5}=\,2\,cm\]You need to login to perform this action.
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