question_answer

A cork is submerged in water by a spring attached to the bottom of a pail. When the pail is kept in a elevator moving with an acceleration downwards, the spring length [EAMCET (Engg.) 1995]            

A)                              Increases            

B)                           Decreases            

C)                         Remains unchanged               

D)                         Data insufficient

Correct Answer: B

Solution :

                            Density of cork = d, Density of water = r Resultant upward force on cork\[=V(\rho -d)\,g\] This causes elongation in the spring. When the lift moves down with acceleration a, the resultant upward force on cork\[=V(\rho -d)(g-a)\] which is less than the previous value. So the elongation decreases.