A Rolling Bat Struck by a Ball

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SUMMARY

The discussion focuses on calculating the position x where a ball strikes a bat to ensure that the tip of the bat's handle remains at (0, 0) after the impact. The bat's moment of inertia is given as J = 0.0530 kgm², and its mass is m = 0.800 kg. The center of mass is located at (0.6 m, 0). The key insight is that the instantaneous velocity of the bat's handle can be zero immediately after the impulse if the distance x is calculated correctly, balancing the rotational movement of the bat with the velocity of the center of mass.

PREREQUISITES
  • Understanding of rotational dynamics and impulse
  • Knowledge of moment of inertia calculations
  • Familiarity with center of mass concepts
  • Basic principles of kinematics
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  • Calculate the impulse required to achieve the desired motion using the impulse-momentum theorem.
  • Study the relationship between angular velocity and linear velocity in rigid body dynamics.
  • Learn about the conditions for static equilibrium in rotating systems.
  • Explore advanced topics in rotational motion, such as torque and angular momentum conservation.
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This discussion is beneficial for physics students, mechanical engineers, and anyone interested in the dynamics of rigid bodies, particularly in understanding the effects of impulse on rotational motion.

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A bat lies along the x-axis so that the tip of its handle is located in (0, 0) while the other end is at (0.9 m; 0). The center of mass is at (0.6 m; 0). A ball hits the bat perpendicularly at (x, 0), causing an impulse I.
The bat’s moment of inertia through the center of mass is J = 0.0530 kgm^2; the bat’s mass m = 0.800 kg.
Calculate x so that the tip of the handle stays at (0, 0) by studying the movement of the center of mass.

I assumed that the axis is parallel with z-axis and that the bat starts rolling around the point (0, 0). I calculated J about the tip of the handle. After that, however, I am stuck since I can only form equations with several unknown variables. Also, I don’t really understand the conditions under which the tip of the handle remains at (0, 0). Have I approached the assignment incorrectly or am I missing something (or both)?

All help is much appreciated.
 
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I think the problem is asking for the distance x, such that the bat handle's tip's instantaneous velocity is zero, immediately after the impulse.

I can guarantee you that the tip of the handle will not stay stay at (0, 0) indefinitely, without other forces involved holding it in place. But its initial, instantaneous velocity can be zero so long as the x is just right. I think that's what you are being asked to calculate.

[Hint: you need to figure out the situation that the rotation movement of the tip, [STRIKE]ωx[/STRIKE] [Edit: I meant ωxc, where xc is the distance from the center of mass to the handle's tip, not to be confused with x, the distance from the tip to the location of the ball striking] is equal and opposite v, the velocity of the center of mass.]
 
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