Work Power and Energy 3 Question 2
2. An ideal spring with spring constant $k$ is hung from the ceiling and a block of mass $M$ is attached to its lower end. The mass is released with the spring initially unstretched. Then the maximum extension in the spring is
(2002, 2M)
(a) $\frac{4 M g}{k}$
(b) $\frac{2 M g}{k}$
(c) $\frac{M g}{k}$
(d) $\frac{M g}{2 k}$
Assertion and Reason
Mark your answer as
(a) If Statement I is true, Statement II is true; Statement II is the correct explanation for Statement I
(b) If Statement I is true, Statement II is true; Statement II is not a correct explanation for Statement I
(c) If Statement I is true; Statement II is false
(d) If Statement I is false; Statement II is true
Show Answer
Answer:
Correct Answer: 2. (c)
Solution:
- In statement I Decrease in mechanical energy in case I will be
$$ \Delta U _1=\frac{1}{2} m v^{2} $$
But decrease in mechanical energy in case II will be
$$ \begin{aligned} & \Delta U _2=\frac{1}{2} m v^{2}-m g h \\ \Rightarrow \quad & \Delta U _2<\Delta U _1 \end{aligned} $$
or statement I is correct. In statement II Coefficient of friction will not change or this statement is wrong.
