Assertion (A): If a pendulum clock is taken to a mountain top, its time period decreases.
Reason (R): Value of acceleration due to gravity is more at heights.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
The time period of a simple pendulum is \(T = 2\pi \sqrt{L/g}\). At a mountain top, the altitude increases, causing the acceleration due to gravity \(g\) to decrease. A decrease in \(g\) leads to an increase in \(T\). Thus, Assertion (A) is false. Reason (R) is also false as \(g\) decreases, not increases, at higher altitudes.
Assertion (A): A small body suspended by a light spring performing SHM. When the entire system is immersed in a nonviscous liquid period of oscillation does not change.
Reason (R): The angular frequency of oscillation of the particle does not change.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
The period of a spring-mass system is given by \( T = 2\pi \sqrt{\frac{m}{k}} \). Immersion in a nonviscous liquid does not change the mass \( m \) or the spring constant \( k \). Hence, the period \( T \) remains unchanged. So (A) is true. Angular frequency is \( \omega = 2\pi / T \), so if \( T \) does not change, \( \omega \) also does not change. So (R) is true and explains (A).
Assertion (A): A simple pendulum is attached on a roof of a elevator. Time period of SHM is \( T \) when elevator is at rest. Time period of SHM must be greater than \( T \) if elevator start moving upward.
Reason (R): Time period of simple pendulum does not depend on acceleration due to gravity.
1. Both (A) & (R) are true and the (R) is the correct explanation of the (A)
2. Both (A) & (R) are true but the (R) is not the correct explanation of the (A)
3. (A) is true but (R) is false
4. Both (A) and (R) are false
View Answer
The time period of a simple pendulum is \( T = 2\pi \sqrt{\frac{L}{g}} \). If the elevator accelerates upward with \( a \), the effective gravity becomes \( g_{eff} = g + a \). The new period is \( T' = 2\pi \sqrt{\frac{L}{g+a}} \). Since \( g+a > g \), then \( T' < T \). So (A) is false. The time period *does* depend on gravity, so (R) is false. Both (A) and (R) are false.