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A bar of length l carrying a small mass ...

A bar of length l carrying a small mass m at one of its ends rotates with a uniform angular speed `omega` in a vertical plane about the mid-point of the bar . During the rotation, at some instant of time when the bar is horizontal, the mass is detached from the bar but the bar continues to rotate with same `omega` . The mass moves vertically up, comes back and reaches the bar at the same point. At that place, the acceleration due to gravity is g

A

This is possible if the quantity `(omega^(2)l)/(2pig)` is an integer

B

The total time of flight of the mass is proportional to `omega^(2)`

C

The total distance travelled by the mass in air is proportional to `omega_(2)`

D

The total distance travelled by the mass in air and its total time of flight are both independent on its mass

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The correct Answer is:
To solve the problem, we need to analyze the motion of the mass \( m \) when it detaches from the bar and how it relates to the rotation of the bar. Here’s a step-by-step solution: ### Step 1: Understand the Initial Conditions The bar of length \( l \) is rotating about its midpoint with an angular speed \( \omega \). When the bar is horizontal, the mass \( m \) is at one end of the bar. The distance from the midpoint to the end of the bar is \( \frac{l}{2} \). ### Step 2: Determine the Linear Velocity of the Mass The linear velocity \( v \) of the mass \( m \) at the moment it detaches can be calculated using the relationship between linear velocity and angular velocity: \[ v = \omega \cdot r \] where \( r = \frac{l}{2} \) (the distance from the pivot to the mass). Thus, \[ v = \omega \cdot \frac{l}{2} \] ### Step 3: Analyze the Motion of the Mass After Detachment Once the mass detaches, it moves vertically upwards under the influence of gravity. The time of flight \( T \) until it returns to the same vertical level can be calculated using the kinematic equations. The mass will first rise to a maximum height and then fall back down. ### Step 4: Calculate the Time of Flight The time to reach the maximum height \( h \) can be found using: \[ h = \frac{v^2}{2g} \] Substituting \( v = \omega \cdot \frac{l}{2} \): \[ h = \frac{(\omega \cdot \frac{l}{2})^2}{2g} = \frac{\omega^2 l^2}{8g} \] The time to reach this height is given by: \[ t_{up} = \frac{v}{g} = \frac{\omega \cdot \frac{l}{2}}{g} = \frac{\omega l}{2g} \] The total time of flight \( T \) (up and down) is: \[ T = 2t_{up} = 2 \cdot \frac{\omega l}{2g} = \frac{\omega l}{g} \] ### Step 5: Determine the Number of Rotations During Time \( T \) While the mass is in the air, the bar continues to rotate. The number of rotations \( N \) made by the bar in time \( T \) can be calculated as: \[ N = \frac{\text{Total angle rotated}}{2\pi} = \frac{\omega T}{2\pi} \] Substituting \( T = \frac{\omega l}{g} \): \[ N = \frac{\omega \cdot \frac{\omega l}{g}}{2\pi} = \frac{\omega^2 l}{2\pi g} \] ### Step 6: Analyze the Proportionality and Independence From the calculations: - The total time of flight \( T \) is proportional to \( \omega \). - The distance traveled by the mass in the air is proportional to \( \omega^2 \). - Both the time of flight and distance traveled are independent of the mass \( m \). ### Conclusion Thus, the correct statements derived from the analysis are: 1. The total time of flight is proportional to \( \omega \). 2. The total distance traveled by the mass in the air is proportional to \( \omega^2 \). 3. The total time of flight and distance traveled are independent of the mass \( m \). ### Final Answer The correct options are A, C, and D. ---

To solve the problem, we need to analyze the motion of the mass \( m \) when it detaches from the bar and how it relates to the rotation of the bar. Here’s a step-by-step solution: ### Step 1: Understand the Initial Conditions The bar of length \( l \) is rotating about its midpoint with an angular speed \( \omega \). When the bar is horizontal, the mass \( m \) is at one end of the bar. The distance from the midpoint to the end of the bar is \( \frac{l}{2} \). ### Step 2: Determine the Linear Velocity of the Mass The linear velocity \( v \) of the mass \( m \) at the moment it detaches can be calculated using the relationship between linear velocity and angular velocity: \[ ...
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