Calculating Torque and Linear Acceleration of a Rotating Rod

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SUMMARY

The discussion focuses on calculating the torque and linear acceleration of a uniform rod of mass M and length L pivoted at one end. The torque when the rod is at an angle θ with the vertical is expressed as -1/2Lmg sin(θ). The linear acceleration of the rod's endpoint when released from the horizontal position (θ=90 degrees) is determined to be 14.7 m/s², derived from the relationship α = -3/2(g/L) and the formula a = αL. The conversation emphasizes the importance of understanding angular acceleration and its relationship to linear acceleration.

PREREQUISITES
  • Understanding of torque and its calculation using T = Iα
  • Knowledge of angular acceleration and its relationship to linear acceleration
  • Familiarity with the moment of inertia for a slender rod pivoted at one end
  • Basic principles of rotational dynamics and Newton's second law for rotation
NEXT STEPS
  • Study the moment of inertia for various shapes and pivot points
  • Learn about the relationship between angular and linear motion in rotational dynamics
  • Explore the derivation of torque equations in different physical scenarios
  • Investigate the effects of varying mass and length on the acceleration of rotating objects
USEFUL FOR

Physics students, mechanical engineers, and anyone interested in understanding the dynamics of rotating systems and the principles of torque and acceleration.

  • #31
-1/2Lmg=1/3 M L^2(alpha) ? is this right?
 
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  • #32
ScienceGeek24 said:
-1/2Lmg=1/3 M L^2(w)^2 ?

There's no w^2. Newton's second law for rotation is ##\tau = I \alpha##
 
  • #33
now, how do i cancel the Ls? one has L and the other one has L^2?? even if i manage to cancel them out i don't get the right answer.
 
  • #34
ScienceGeek24 said:
now, how do i cancel the Ls? one has L and the other one has L^2?? even if i manage to cancel them out i don't get the right answer.

You're not done yet. Solve for ##\alpha##. What expression do you get?
 
  • #35
α=-1/2g-1/3L
 
  • #36
ScienceGeek24 said:
α=-1/2g-1/3L

Something went wrong there... You started with

-1/2Lmg=1/3 M L^2(alpha) (assuming m is really M)

How did you end up with two terms? Try that again.
 
  • #37
sorry! i mmeant α=-1/2g/1/3 I got the answer! 14.7 m/s^s thanks man!
 
  • #38
ScienceGeek24 said:
sorry! i mmeant α=-1/2g/1/3 I got the answer! 14.7 m/s^s thanks man!

##\alpha = -\frac{3}{2}\frac{g}{L}##

You've still got the L in the denominator to deal with. It goes away when you calculate the linear acceleration of the endpoint... ##a = \alpha L##.
 
  • #39
oh got it! thanks bro!
 

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