question_answer

A rod AB of mass 10 kg and length 4 m rests on a horizontal floor with end A fixed so as to rotate it in vertical plane about perpendicular axis passing through A. If the work done on the rod is 100 J, the height to which the end B be raised vertically above the floor is

A)  1.5m                                    

B)  2.0m    

C)         1.0m                    

D)         2.5m

E)  3.0m

Correct Answer: B

Solution :

Work done \[=\frac{mgh}{2}\] \[\therefore \]  \[100=\frac{10\times 10\times h}{2}\] Or           \[h=2.0\,m\]