3 forces acting on a conical pendulum
- Gravity(=mg): The force the Earth pulls.
- Tension: The force applied to both ends of the thread. Tension is always directed to the center from both ends.
- Centripetal force(Fc): The force that maintains circular motion. The centripetal force always toward the center of rotation.
Fc=mrω2=mr(2πT)2Fc=mrω2=mr(2πT)2
ω: Angular velocity of rotational motion (rad/s)
T: period of rotational motion (seconds)
Find the period of a conical pendulum
Consider a conical pendulum with a line length ‘L’ and a rotation radius ‘r.’
Centripetal force(Fc) is the result of gravity and tension. Also, the centripetal force is perpendicular to gravity. From this, the following equation is calculated.
Fc=mg⋅tanθFc=mg⋅tanθ
Substituting the definition of centripetal force comes the following equation.
mr(2πT)2=mg⋅tanθmr(2πT)2=mg⋅tanθ
(2πT)2=gr⋅tanθ(2πT)2=gr⋅tanθ
Since it is tanθ=rhtanθ=rh, we can make it a bit simpler.
(2πT)2=gh(2πT)2=gh
Solving the above equation for the period T, It becomes as follows.
T=2π√hgT=2π√hg