question_answer

Two masses A and B are connected with two inextensible string to write constraint relation between \[{{v}_{A}}\] and \[{{v}_{B}}\].       Student A:  \[{{v}_{A}}\,\cos \theta ={{v}_{B}}.\] Student B: \[{{v}_{B}}\,\cos \theta ={{v}_{A}}.\]

A)  A is correct, B is wrong

B)  B is correct, A is wrong     

C)  Both are correct       

D)  Both are wrong    

Correct Answer: A

Solution :

   If student will use vector component (only mathematically) he/she may conclude both are correct. Hence the option [c].     Correct concept: Velocity of both ends of the string along the length of the string should be same.