Question
Question: A cork is submerged in water by a spring attached to the bottom of a pail. When the pail is kept in ...
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
A
Increases
B
Decreases
C
Remains unchanged
D
Data insufficient
Answer
Decreases
Explanation
Solution
Density of cork = d, Density of water = ρ
Resultant upward force on cork=V(ρ−d)g
This causes elongation in the spring. When the lift moves down with acceleration a, the resultant upward force on cork=V(ρ−d)(g−a) which is less than the previous value. So the elongation decreases.
