question_answer

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

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. \[{{v}_{B}}={{v}_{A}}\cos \theta .\]